COLUMN ONE : Putting the Squeeze on Nogales : Crackdowns in San Diego and El Paso have sent illegal immigrants streaming through this Arizona town, which is separated by only a fence from its Mexican neighbor. Chaos and violence have followed.

The quaint narrow streets of the aging downtown here have become a strange urban theater of pursuit and confrontation.

On a recent afternoon, illegal immigrants carrying babies and duffel bags streamed over the international fence, chased by Border Patrol agents through the bustling Latino crowds at McDonald’s, Burger King and Holy Cross Hospital. A freight train ran over a border-crosser, chopping off his foot. And Border Patrol agents with drawn guns arrested two knife-wielding men who were robbing illegal immigrants.

Another day in Nogales--the newest gateway for illegal immigration on the Southwest border.

The frenzied scene results partly from a buildup of fortifications and agents in San Diego and El Paso, which together traditionally have accounted for about 65% of illegal crossings, according to U.S. and Mexican officials. The Border Patrol has based its strategy on the stark geography of the nearly 2,000-mile border: The bleak, hostile expanses of deserts and mountains form a natural barrier, funneling most illegal immigrants to a few urban corridors.

Bolstered defenses in the two main corridors have begun to redirect the flow of migrants east from San Diego and west from El Paso to Arizona, where Border Patrol arrests doubled to a record-breaking 139,473 last year, officials say.

“It is what was expected,” said Raul Lopez Lira Castro, the Mexican consul in Nogales. “Because they have difficulty crossing in San Diego, those going to Los Angeles or Chicago come through here.”

Even as arrests and violence decline elsewhere, Nogales and its namesake city on the Mexican side of the line are experiencing the chaos that peaked in San Diego and El Paso several years ago. Rampant crime against illegal immigrants spurred Mexico to create an offshoot of Grupo Beta, the elite Tijuana border police unit, in the Mexican Nogales last year.

The influx of a vulnerable population and attendant social problems have afflicted these symbiotic towns, known as ambos (both) Nogales, which are bound by economic and family ties. Unlike the canyons of San Diego or the river in El Paso, there is no natural buffer. U.S and Mexican neighborhoods of closely packed, brightly colored houses flow across the hillsides into each other, interrupted fleetingly by the international line.

“It’s just a fence that happens to run right down the middle and break us in two,” said Louie Valdez, 23, an earnest college student who was recently elected mayor of the U.S. Nogales. He says the citizens of the overwhelmingly Latino town, many of whom have relatives across the line, sympathize with immigrants. But they are fed up with violence and tension--on three successive days in December, gunmen fired on U.S. officers from across the border.

When U.S. Atty. Gen. Janet Reno toured Nogales this month to announce a 30% increase of Border Patrol forces in Arizona--she described the state as the “side door” to California--her caravan was pelted by rocks from Mexican territory. Gustavo De La Vina, western regional director of the Immigration and Naturalization Service, was reminded of the anarchic days in 1991 when he became the Border Patrol chief in San Diego.

“It was a real flashback,” De La Vina said. “You see groups entering unimpeded. Rock barrages. No delineation of the border. It’s just like history repeating itself.”

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As Border Patrol agents released Manuel Maldonado through a pedestrian turnstile separating the two downtowns last week, the genial 26-year-old bartender said he had crossed previously from Tijuana to Los Angeles, but decided to try Nogales this time.

“The migra (INS) is tougher there in California, since they put in the (Proposition) 187 (law),” said Maldonado, who also has worked in Minneapolis and Tacoma, Wash. “The people are starting to cross here. But you have to be careful. There’s a lot of robbers. They stab you, take your sneakers and jacket and dump you in a canyon.”

Advocates fear that illegal immigrants testing their luck in this volatile region will run into a thicket of dangers: criminal marauders, abusive U.S. and Mexican law enforcement, ruthless drug traffickers and punishing weather and terrain.

“It is a longer, more complicated and more dangerous journey, because the desert is another enemy,” said Consul Lopez.

Referring to the North American Free Trade Agreement, which took effect last year, he added that the U.S. crackdown at the border seems contradictory. “We sign a commercial treaty and the response is 100 more agents and a (border) fence. This could create more tension.”

Border Patrol commanders say the numbers show the need for reinforcements, however. Arrests by the agency’s Tucson sector, which covers most of the state, jumped 51% last year and about 70% this month. For the first time, Tucson ranked above El Paso, where arrests dropped after a blockade by Border Patrol agents concentrated on the north bank of the Rio Grande.

San Diego remains the key route for Mexican immigrants to the employment and cultural hub of Southern California: The Border Patrol in San Diego led all sectors with more than 450,000 arrests in 1994. But Tucson recorded an extraordinary fivefold increase in apprehensions of non-Mexican immigrants during the last three months. These Central Americans, Eastern Europeans and Asians represent a fraction of total arrests, but they pay exorbitant smuggling fees. And their growing presence indicates that sophisticated smugglers regard Arizona as the corridor of choice, according to observers in the United States and Mexico.

Critics accuse the Border Patrol of exaggerating the shift to Arizona to win more resources for the Tucson sector. Human rights activists and Mexican academics say the Border Patrol has proved adept at cranking up arrests to make the problem look worse than it is.

“There definitely has been an increase in arrests because of an increase in enforcement,” said Jesus Romo Vejar, a Tucson civil rights lawyer. “But there is insufficient evidence to conclude that this translates into an increase in the numbers of immigrants.”

Border Patrol agents concede that more agents have been deployed in downtown Nogales for the past year, leading to more arrests. But they say they are not manipulating statistics.

“That’s bunk,” said Bart Schneider, a supervisory intelligence officer in Tucson. “We need the agents. . . . The aliens we interview like this corridor because they can use the airports in Tucson and Phoenix to go wherever they want. They found out in the Mexican media that there was pressure in El Paso and San Diego, and Nogales was a target of opportunity.”

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Scandals have worsened distrust of the Border Patrol. In one notable 1992 case, an agent was charged with murdering a fleeing suspect and finally convicted of assault in another case.

The problems continue. Agent Raul Teran of Nogales was arrested in November and accused of molesting a 12-year-old girl. A legal U.S. resident recently alleged that she was sexually assaulted by an agent who is serving time for conviction in a similar incident. And prosecutors in Cochise County, in the southeast corner of Arizona, say they are still investigating Agent Mark Martinez in the execution-style murders of two men after a party in the desert.

“We’ve had some bad apples,” said senior agent Kevin Oaks, 35. “But the citizen cooperation is improving again.”

Some illegal border-crossers are not even immigrants in the classic sense, Oaks said. For years, they have slipped across to shop, sell tortillas and limes or fill water buckets at the garden hoses of friendly U.S. neighbors. Oaks sometimes does not leave his vehicle to stop them; he waved a vendor on an ancient bicycle back to Mexico and cheerfully asked Sinaida Contreras and her husband, Martin Pedroza, to climb aboard.

“Why don’t they let us go?” asked Contreras, an 18-year-old with billowing red hair who was noticeably pregnant under her baggy warm-up jacket. “All we want to do is go shopping and then we’ll go home.”

Agent Oaks cruised past the home of his in-laws, a prominent Nogales family descended from Mexican immigrants. The pleasant ridge-top house has been burglarized, set on fire and hit by gunfire--the price of a commanding view of the nearby border. Bars and gates enclose neighboring houses. Recently, a man was convicted in Mexico of killing a 6-year-old girl, who was slain in her home by an errant bullet from a border gunfight.

Rather than the immigrants, Oaks blames the smugglers, bandits and other predators whom Nogales increasingly attracts--along with continuing drug activity. The “tunnel kids” are a particularly grim subculture: young scavengers who live in cross-border sewer tunnels. They get high on paint fumes and brush their teeth in the disease-infested muck. They also mug illegal immigrants sneaking northward.

“They get the younger kids to act like guides, then they rob (the crossers) with broken bottles, clubs, rocks,” said Joe Flores, a tall agent who rides with the Border Patrol’s bicycle unit. “I’ve seen full-grown men intimidated into giving up their money.”

About noon, Flores watched in disbelief from the street above a tunnel entrance as a youth jumped a border-crosser and put a knife to his throat. Flores drew his gun and ordered the assailant to drop the knife; the youth pulled his victim into the line of fire, using him as a shield, then sprinted into the tunnel. Agents chased him down.

Later, the youth sat chained to a bench in the shabby and cramped Nogales Border Patrol station--a former Volkswagen dealership. He said he had lived in the state of Guanajuato and in Escondido, Calif. He claimed to be 17. His jeans and hooded jacket were muddy, his face sullen, his eyelids heavy from sniffing paint, which he buys for $3 a can.

The youth said the agents had caught the wrong guy. But he admitted that the wicked-looking knife was his.

“It’s an 007 model,” he said, eyes brightening. “I just bought it yesterday.”

In an example of cross-border cooperation, the two Nogaleses have teamed up to build a shelter on the Mexican side for the tunnel children, many of them former migrants swallowed up by the border nether world.

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Even more than El Paso, where the downtowns face each other across the Rio Grande, the action in Nogales plays out in plain view on a four-mile border strip. Agents routinely hunt down suspected illegal crossers in shops and restaurants where smugglers, including some of the town’s legion of taxi drivers, offer rides to Tucson, Phoenix and points beyond for up to $1,000.

The skirmishes inevitably bring complaints by business owners, who depend on Mexican clients. Fears about offending Mexican officials and visitors led city leaders to agree to replace or augment the steel border fence with a more “aesthetically pleasing” barrier. They also asked Reno to speed the application process for border-crossing permits, in hopes of reducing the casual, short-range fence-jumping.

“We want to vigorously enforce the laws, but facilitate legal entry,” said Mayor Valdez, whose father is a retired construction worker born in Mexico.

Valdez articulates the ambivalence felt by many in Nogales. He denounces as “completely racist” a proposed Arizona version of California’s Proposition 187. But he sees no contradiction between that stance and his support of a Border Patrol crackdown.

Illegal immigration “taxes our municipal resources and strains our operations,” he said. “If they can blockade San Diego and El Paso, they can blockade Nogales as well. We are in a more precarious situation.”

More than in larger border cities, the influx here poses a considerable burden for the combined Nogales region. The population numbers only about 25,000 on the north and about 250,000 on the south.

“The pain the migrants cause is not as bad as the pain they suffer,” said Josefina Guerrero, a human rights activist who runs a center for crime victims on the Mexican side. “But these cities are not ready to handle either massive deportations or the increased flow of migration from California and Texas.”

Border Patrol officials, meanwhile, hope that increased agents and funds will impose a degree of control. Currently, limited detention space precludes even the illusion of punishment that exists in San Diego, where prisoners spend up to eight hours in a cell.

In Nogales, agents simply fill out the forms on the spot and drop off their prisoners at the border crossing.

“For the agents, it’s kind of frustrating right now,” Agent Oaks said.

Agents arrested several groups twice during one recent afternoon, including Miguel Resendiz and two other long-haired, neatly dressed men from central Mexico. They were arrested on foot and sent south, then promptly crossed again and were caught in a rusty blue Pinto. Both the agents and the immigrants grinned at the absurd reunions.

Resendiz, a 24-year-old father of two who had worked as a ranch hand in Oklahoma, said Mexico’s economic crisis left him no choice but to keep trying. His voice soft and urgent, he said: “We know we are violating the law. But if I speak the truth perhaps I can get a work permit. We just want to work. This (peso) devaluation made things very hard.”

Ultimately, the shift of migration toward Arizona--if it continues to develop--will help realize the U.S. government’s border control strategy. But official policies have human consequences: The forbidding deserts here have claimed numerous lives of border-crossers, some of whom try to walk the 65 miles to Tucson.

Among the casualties: an 8-year-old boy named Jaime Ramirez Leon. In 1990, he was accidentally left behind in the desert by smugglers who were driving his family north in two cars. He wandered to a remote house to ask for help two weeks later. But a woman at the house fired a gunshot into the air and he ran away.

Hunters found Jaime’s body in a cave where he took refuge and died of exposure after a month in the wilderness.