TAPACHULA, Chiapas (AP) — At least 10 migrants have died and about 15 other people were injured when a freight truck they were riding in crashed on a highway in southern Mexico near the border with Guatemala.

It was the latest in a series of migrants deaths in Mexico amid a surge in migrants traveling toward the U.S. border.

The civil defense office of the state of Chiapas said the truck crash happened Sunday on a highway near the town of Pijijiapan, about 110 miles (175 kilometers) from the Guatemalan border.

The office posted photos showing a small truck with an open cargo box tipped on its side, and victims thrown onto the side of the highway.

The office did not confirm the nationalities of the victims, but an employee of the state prosecutor’s office said they were largely Cuban migrants who had been hitching rides on passing vehicles. The employee was not authorized to speak on the record.

It was also not clear how many of the 15 injured were migrants. There was no immediate information on their condition, or nationalities.

Mexican authorities generally prohibit migrants without proper documents from riding buses, so those without the money to hire smugglers often walk along the side of highways, hitching rides aboard passing trucks.

There have been a number of migrant deaths over the last week.

A migrant from Ecuador died and 10 others from Colombia and Guatemala were injured in an crash Saturday that occurred while they were being taken for processing in a van operated by Mexico’s immigration agency.

Mexico’s National Migration Institute said the van was involved in a collision with a bus in the the city of Mexicali, across the border from Calexico, California.

On Friday, two Mexican migrants were fatally shot on the Mexican side of the border and three others suffered gunshot wounds, the Migration Institute said. Rescue services found a group of 14 Mexican nationals at dawn on Cuchuma Hill near Tecate, a city between Mexicali and Tijuana.

The cause of the shooting wasn’t 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.

And on Thursday in Chiapas, a truck flipped over on the highway, killing two Central American migrants and injuring another 27.

The Migration Institute said Friday that 52 migrants were traveling in an overcrowded dump truck when the driver lost control and overturned. The injured, including six children, were transported to hospital, where they were all granted legal cards of asylum, as victims of a crime on Mexican territory.

And on Wednesday, two Central American migrants died after trying to board a moving train in the state of Coahuila near the Texas border.