MEXICO CITY — Mexico’s National Guard shot dead two Colombians and wounded four others in what the Defense Department said was a standoff near the U.S. border.

The shootings occurred Saturday on a dirt road near Tecate, east of Otay Mesa on the California border, which is frequently used by Mexican migrant smugglers, the department said.

It was unclear if the Colombians were migrants, but a Colombian who was not injured in the shooting was handed over to immigration officials, suggesting they were.

Mexico’s Department of Defense, which controls the National Guard, did not respond to requests for comment on this point.

If they were migrants, it would mark the second time in just over a month that military forces have opened fire and killed migrants.

On October 1, the day President Claudia Sheinbaum took office, soldiers opened fire on a truck, killing six migrants in the southern state of Chiapas. An 11-year-old girl from Egypt, her 18-year-old sister and a 17-year-old boy from El Salvador died in that shooting, along with people from Peru and Honduras.

Describing the events near Tecate on Saturday, the Department of Defense said in a statement late Sunday that a militarized National Guard patrol was attacked after spotting two trucks in the area.

A truck sped off and escaped. The National Guard opened fire on the other truck, killing two Colombians and wounding four others. There was no immediate word on their condition and no casualties among the guards involved.

A Colombian and a Mexican were found and detained unharmed at the scene, and departments said officers found a handgun and magazines commonly used for assault rifles at the scene.

Colombians have sometimes been recruited as gunmen for Mexican drug cartels, which are also heavily involved in migrant trafficking. But the fact that the survivor was handed over to immigration officials and that the Department of Foreign Affairs contacted the Colombian consulate suggests they were migrants.

Cartel gunmen sometimes escort or kidnap migrants as they travel to the US border.

The three National Guard officers who opened fire have been removed from duty.

Former President Andrés Manuel López Obrador, who left office on September 30, gave the military an unprecedented role in public life and law enforcement; created the militarized Guard and used combined military forces as the country’s main law enforcement agency, replacing the police. The Garda has since been placed under the control of the army.

But critics say the military is ill-equipped to do civilian law enforcement work. Moreover, the lopsided death toll in such clashes – where all the deaths and injuries are on one side – raises suspicions among activists about whether there really was a confrontation.

For example, the soldiers who opened fire in Chiapas—who have been detained pending charges—claimed they heard “detonations” before they opened fire. There was no indication that any weapons were found at the scene.