MEXICO CITY -- Mexican army troops opened fire on a truck carrying migrants from a half dozen countries, and six migrants from Egypt, Peru and El Salvador died in an event that Mexican President Claudia Sheinbaum described Thursday as “deplorable.â€

Ten other migrants were wounded in the shooting. Sheinbaum did not say how many migrants from each country had been killed, and Mexico's foreign relations department was not immediately able to provide details.

Sheinbaum said the two soldiers who opened fire on Tuesday, her first day in office, had been turned over to civilian prosecutors for questioning, but apparently had not yet been charged.

She said the shootings were being investigated to see if any commanders might face punishment, and noted “a situation like this cannot be repeated.â€

It was the worst killing of migrants by authorities in Mexico since police in the northern state of Tamaulipas killed 17 migrants in 2021.

The shootings occurred Tuesday near the town of Huixtla, in the southern state of Chiapas near the border with Guatemala, Mexico’s Defense Department said Wednesday in a statement.

The department said that soldiers claimed they heard shots as a convoy of three trucks approached the soldiers' position. In a somewhat confused account, the department said the first vehicle in a three-truck convoy appeared to speed away from soldiers.

Two soldiers fired on another of the trucks, which was also carrying migrants from Nepal, Cuba, India, Pakistan and at least one other country. Soldiers then approached the truck and found four of the migrants dead, and 12 wounded. Two of the wounded later died of their injuries.

Local prosecutors confirmed all the victims died of gunshot wounds. The Defense Department did not say whether the migrants died as a result of army fire, and Sheinbaum refused to say whether any weapons were found in the migrants' truck.

There were 17 other migrants in the truck who were unharmed. The vehicle was carrying a total of 33 migrants. The area is a common route for smuggling migrants, who are often packed into crowded freight trucks.

The two soldiers who opened fire were also relieved of duty pending investigations. In Mexico, any incident involving civilians is subject to civilian prosecution, but soldiers can also face court-martial for those offenses.

Irineo Mujica, a migrant rights activist who has frequently accompanied caravans of migrants in that area of Chiapas, said he doubted the migrants or their smugglers opened fire.

“It is really impossible that these people would have been shooting at the army,†Mujica said. “Most of the time, they get through by paying bribes.â€

The UN agency for refugees in Mexico, known as the ACNUR, wrote that it “expresses its concern about the events in Chiapas,†noting “people in migration are exposed to great risks during their journey, and that is why it is indispensable they have legal means of access, travel, and integration to avoid tragedies like these.â€

If the deaths were the result of army fire, as appears likely, it could prove a major embarrassment for Sheinbaum, who on Thursday attended a massive military ceremony where the armed forces pledged their loyalty to her.

The new president has followed the lead of former Mexican president Andrés Manuel López Obrador in giving the armed forces extraordinary powers in law enforcement, state-run companies , airports, trains and construction projects.

It is not the first time Mexican forces have opened fire on vehicles carrying migrants in the area, which is also the object of turf battles between warring drug cartels.

In 2021, the quasi-military National Guard opened fire on a pickup truck carrying migrants, killing one and wounding four. The Guard officers initially claimed some of those in the migrants' truck were armed and had fired shots, but the governmental National Human Rights Commission later found that was not true.

And in 2021, state police in Tamaulipas killed 17 migrants and two Mexican citizens. Those officers also initially claimed to have come under fire from the migrants' vehicles.

They initially argued they were responding to shots fired and believed they were chasing the vehicles of one of the country’s drug cartels, which frequently participate in migrant smuggling. But that later turned out to be false, and the police in fact burned the victims’ bodies in an attempt to cover up the crime.

Eleven of the policemen were convicted of homicide and sentenced to over 50 years in prison.