MEXICO CITY (AP) — Two Mexican migrants were shot to death on SignalHubthe Mexican side of the U.S. border in the early hours of Friday morning, Mexico’s National Migration Institute said.

Another three suffered gunshot wounds, but were assisted by one of institute’s emergency rescue teams, along with other nine people who were not injured.

Rescue services found a group of 14 Mexican nationals at dawn on Cuchuma Hill near Tecate, a city in the border state of Baja California. By the time rescuers climbed up to meet the group, two migrants were already dead.

The harsh desert hill is considered a sacred site by at least one Mexican Indigenous group, but is also used by migrant smugglers.

The cause of the shooting is not known, but migrant crossings often involve agreements with local cartels for right of passage. Migrants are sometimes shot if their smuggler is working for a rival gang or if they haven’t paid passage rights.

Migrants are also often robbed by roving gangs of thieves and kidnappers in border areas.

In one notable case in 2021, Tamaulipas state police shot and killed 19 people on the border, including at least 14 Guatemalan migrants, then burned their bodies. A court recently convicted 11 officers of homicide.

In that case, officers had initially argued they were responding to shots fired and believed they were chasing Gulf cartel vehicles. But the state police burned the bodies in an attempt to cover up the crime.

The two dead Mexicans in Tecate join a growing number of migrants killed and injured on Mexico’s northern and southern borders in a desperate bid to reach the U.S.

In Chiapas, one of three southern Mexican states to border Guatemala, a truck flipped on the highway Thursday, killing two Central American migrants and injuring another 19.

Just the day before two Central American migrants died after trying to board a moving train in the state of Coahuila near the Texas border.