On Mexican as Well as U.S. Side, Traffic Takes Toll on Migrants : Border: A busy highway and illegal immigration provide a lethal mixture again as four people are killed.

A high-speed roadway passes close to the U.S.-Mexico border. Scores of would-be immigrants have been run down--and many killed--while attempting to run across the road while en route north. Authorities have posted signs alerting pedestrians of the hazard.

The scenario is familiar to motorists and law enforcement authorities in San Diego, where more than 100 illegal immigrants have been killed during the past five years while trying to negotiate Interstate 5 and other area freeways on foot.

However, a similar scene has been enacted with numbing regularity in recent years along Tijuana’s Avenida Internacional, which parallels the border fence west of downtown and has been the site of many accidents causing the deaths and serious injuries of migrants headed north.

On Tuesday evening came the worst yet: A car traveling along the four-lane avenue attempted to avoid pedestrians running across the road and instead plowed into a group of people massed near the international boundary and planning to cross illegally. The impact killed four and injured five others, scattering victims on both sides of the border in an incident that authorities said was unusual only for its severity--and because dead and injured wound up in both nations.

“It’s a very dangerous area for immigrants,” said Capt. Jorge Alberto Gonzalez Higuera of the Tijuana municipal police.

The strip just to the north of the highway is a major staging point for border-jumpers, who frequently scamper back and forth across four lanes of high-speed traffic, often in the dark. The avenue, which connects the downtown to the beach area and to the toll road that leads to Ensenada, is a major east-west thoroughfare.

Mexican authorities say the hazard is not unlike the more-publicized threat faced by immigrants north of the border who attempt to cross Interstate 5 and other California freeways on foot. U.S. authorities have posted warning signs and taken other precautionary measures, but the toll of death and injury keeps mounting.

“What happens on la avenida is just like what happens in California,” said Cmdr. Vicente Corona of the Federal Highway Police in Tijuana.

Mexican authorities say the avenue suffers from another hazard: High-powered lights installed by the U.S. Border Patrol in the Tijuana River levee area sometimes almost blind motorists, increasing the possibility of an accident, said Capt. Gonzalez of the Tijuana police. In addition, dust churned up by Border Patrol vehicles in the levee area has been known to send thick clouds onto the avenue, further obscuring vision.

However, Tuesday’s accident happened about 6 p.m., when visibility was not a problem.

The driver, Jose Castro Rivera, 28, who according to authorities has residences in both Tijuana and San Diego, did not appear to be at fault in the incident, authorities said. Castro was guiding his vehicle along Avenida Internacional at the legal speed limit--60 kilometers an hour, or 36 m.p.h.--and showed no evidence of being intoxicated, Cmdr. Corona said.

The car swerved in an effort to avoid pedestrians on the freeway, police said. But Castro lost control and smashed into a group of perhaps a dozen people gathered on the northern end of the roadway, atop a retaining wall that roughly marks U.S. territory, police said.

The vehicle, which was headed toward the Playas de Tijuana area, ended up on the U.S. side, after having plunged over the 12- to 15-foot wall. Victims went flying in both directions, police said.

Officials said that Castro could still theoretically be charged with vehicular homicide or other infractions under Mexican law. The federal attorney general’s office is investigating the matter and should make its decision within a few days, authorities said. Meantime, Castro will remain in custody in Tijuana, authorities said.

In the immediate aftermath of the accident, authorities said, Mexican police and emergency personnel crossed the border in an effort to provide assistance to the injured. Mexican firefighters positioned a ladder down the retaining wall leading to U.S. territory. Castro, who escaped serious injury, exited his vehicle, stunned, on the U.S. side.

His subsequent return to Mexico has been a source of considerable speculation--and controversy.

According to Corona of the Mexican Federal Highway Police, Castro agreed voluntarily to return to Mexico in the company of Mexican officers.

But U.S. Border Patrol officials wondered aloud whether Castro wasn’t coerced into going back. Steven Kean, a supervisory Border Patrol agent in San Diego, stated that Castro was returned to Mexico “under questionable circumstances.”

The comments reflect the sensitivity in both nations to cross-border incursions by law enforcement officers of either nation.

Sept. 14, a Border Patrol agent attempting to arrest an illegal immigrant in San Diego briefly crossed into Mexican territory, drawing an official protest from Mexico City. Border Patrol officials said the agent entered Mexican territory inadvertently during a struggle with a suspect.

In Tuesday’s incident, all four persons killed--three men and one woman--remained unidentified as of late Wednesday.

Two men killed and thrown onto the U.S. side were believed to be in their late 20s, according to the San Diego Medical Examiner’s office. In Tijuana, a female victim was believed to be about 20 years old, and a third male was about 30, officials said.

Among the injured on the U.S. side, Francisco Tinoco, 20, remained in critical condition at UCSD Medical Center, where an unidentified 22-year-old male victim was listed in fair condition. A third injured man, Reyes Morales, 32, was in serious condition at Mercy Hospital with a fractured pelvis, a hospital spokesman said.

At the Red Cross clinic in Tijuana, two injured men--Isidro Hernandez, 20, of Fresno, Calif., and Juan Carlos Salas, a teen-ager whose precise age and address were not available--were in stable condition with various injuries, a spokeswoman said. Both are expected to recover.

Times staff writer Lisa Castiglione contributed to this report.