Patrolling a land of secret signals and signs on the Texas-Mexico border

The report came over the radio from a Border Patrol agent perched on the riverbank: “We’ve got a raft with five bodies on it. Roma, upriver from the bridge. I cannot see them; I just know they’re already on the U.S. side.”

Supervisory Agent Albert Olivares drove toward the action.

“Sounds like the group hit a bug,” he said, slang for tripping a sensor planted in the thick mesquite brush.

Within minutes, half a dozen agents descended on nearby Water Street, about a block north of the Rio Grande. One brought a tracking dog, a German shepherd named Arys.

Such scenes unfold routinely in Roma, a town of 11,400 people on the Mexico border. It’s a well-traveled entry into Texas’ Rio Grande Valley, the country’s busiest corridor for illegal immigration.

If immigrants can cross the river here without being spotted, it’s not difficult to clamber up the bank to hide in or around homes. They can run a few blocks to a strip mall, try to blend in with shoppers, or meet smugglers’ cars on Highway 83. Agents call that brief window “vanishing time.” Residents are so used to the cat-and-mouse of Border Patrol and immigrant that they barely look up as desperate dramas unfold around them.

On this steamy summer day, agents fanned out on Water Street, radios crackling again, this time with reports from a white aerostat blimp hovering above and agents across town.

“They didn’t go north, they didn’t go south. They doubled back, or they’re in the houses,” an agent said.

The blimp relayed images captured overhead to agents at controls on the ground, who updated those in the field.

Arys picked his way across an overgrown lot and led agents to the back of a tan brick house built into a hill. The owners had added a basement of gray cinder blocks to the hillside, with “Mexico” stamped on its side. Agents tried one of two black metal doors. It held, sizzling in the tropical sun.

“Open the door!” the dog handler, Ronnie Montemayor, shouted in Spanish.

The door didn’t budge.

“It’s going to get very hot, and we’re not leaving,” he said. Silence.

Radios buzzed again. Another raft had been spotted crossing the river. Though immigrants sometimes cross in the dead of night, here the days are just as busy. It was now about 11 a.m., the sun blazing.

Several cars drove past the developing crime scene, which didn’t strike the agents as odd. What bothered them was a man in a dark gray van that lingered a block away, watching. Before they could question the man, he drove off.

Roma is famous for smuggling. Agents have trouble trusting residents, who they fear might work for Mexican cartels. Instead of cultivating neighbors, agents remain outsiders, on edge, relying on technology and subtle signs to do their job.

They ride horses, bicycles and boats down the river where smugglers’ scouts pose as fishermen. They follow footprints like animal trackers, dragging roads with tires so that fresh prints stand out. One day an agent took a wooden plank and, like a groundskeeper dragging an infield, smoothed out dirt in a resident’s backyard.

Agents also have learned to listen, patrolling trails that are as thick with the calls of smugglers as the chaparral. A nightly chorus of smugglers’ whistles, shouts and truck horns tell immigrants that it’s time to move.

There were no sounds coming from the basement where agents waited with Arys. Agents called Roma police to see who owned the house as they picked their way around a backyard play set and basketball hoop. Neighbors said it was a family. Agents finally reached them by phone. They were not surprised to hear migrants were hiding in their basement.

“They’ve done it before,” Olivares said.

Three agents tried to force the basement door, pushing with all their strength. It held. An agent got down on his knees to peer underneath. He saw a shoe, and a drop of sweat.

“Open the door. I see you. You’re going to die without water,” the agent shouted, banging on the hot metal.

The door opened a crack. Agents pulled three men into the weedy yard. Two of them, ages 23 and 17, were from Mexico. The third was Guatemalan. Jose Luis Garcia Morales initially spoke an indigenous language, Quiche, thinking one of the agents looked Guatemalan. He wasn’t.

Garcia reverted to Spanish, explaining that he had traveled more than 1,600 miles north from Coatepeque to feed his family. He had just 20 pesos left, about $1.

“We all have children, parents,” he said. He pointed at the agent. “You too have a heart. You’re working to eat. So are we.”

The agent moved to load Garcia into a waiting van.

“Look,” Garcia whispered. “Let me go.”

“I can’t.”

Garcia boarded the van.

Apprehensions don’t always go so smoothly.

A year ago this month, a man Olivares was apprehending tried to grab his gun. He was saved by a safety holster. Olivares also responded last year to a call for help from agents on horse patrol who had found a heavyset migrant in distress on a nearby ranch.

“He had a very weak pulse,” Olivares recalled. The man died in his truck before they could reach a hospital.

After capturing the three immigrants, Olivares drove east to the other side of town, past a house that agents call “radio man’s” because the owner’s father foiled law enforcement radio frequencies to smuggle drugs. He pointed out other landmarks, reciting nicknames agents had given them: dead dog corner, shot-up wheelbarrow, cake shop and Speedio’s, a long-shuttered car wash.

When there are no street addresses for a given location, it’s easier to say they’re at the cactus patch or outhouse. Agents create some signposts of their own in the brush: an old doll jammed atop a roadblock; a Darth Vader mask nestled in a pecan tree trunk; scarecrows perched on the riverbank.

Agents also monitor popular smuggling pick-up spots, like the Burger King on Highway 83.

“You’ll see them eating a Whopper,” said Olivares, 48, who grew up in the Rio Grande Valley and joined the Border Patrol in 1997.

He’s seen smugglers dress up as UPS deliverymen, priests and pilots, “wings and all.” The smugglers know when the Border Patrol makes shift changes and view them as opportunities to cross the river.

“They’re watching the aerostats as much as we do,” Olivares said of smugglers. They wait until the blimps are routinely grounded to move groups of people or loads of drugs from stash houses across the river.

Days later, a pair of Border Patrol motorboats zoomed down a stretch of the Rio Grande to the east. When they saw fishermen on the Mexican riverbank, they slowed.

Agents lobbed casual questions in Spanish: What have you caught? Is the fishing good? As the fishermen spoke, agents photographed them and their Texas license plates. The men were loaded with gear, unlike others agents had seen posing with crude sticks and strings. One even had a clutch of bass. But agents were still suspicious. If they lived in Texas, why fish from the opposite bank, at strategic bends overlooking stretches of river favored by migrants?

“Usually if anyone is hanging out here, they’re scouting” for smugglers, Agent C. Hernandez said.

As agents guided the boats upriver, they leaned against plastic-coated cables running from the front of the boat to the top, designed to foil the wires that smugglers string across the river to catch them unawares. They call them “decapitation lines.”

When they heard a raft had just crossed near Los Ebanos, the boats took off. Los Ebanos, a town downriver named after a stand of ebony trees, is home to the oldest hand-drawn ferry on the river, which carries a few cars and pedestrians across to a U.S. customs booth.

By the time the boats arrived, they found a muddy trail up the U.S. riverbank. Migrants had just scrambled out of sight. The smuggler’s raft had vanished.

“They’re probably watching us right now to see if we catch those guys,” said Agent A. Martinez.

Agents headed up the trail to an overgrown cemetery. They pointed to a fresh wavy sneaker print called a “running W.”

“They hugged the brush line past the cemetery,” an agent said.

“They’ll call ahead and have someone pick them up,” another added.

The river agents radioed counterparts on the other side of the cemetery, on horse patrol. There was noting to do but return to their boats. From there, they set out once again, coasting west, scanning the dense banks for smugglers.

molly.hennessy-fiske@latimes.com

@mollyhf