Mexican authorities said over the weekend they recovered 19 bodies, some burned and shot, in a vehicle left in an uninhabited region of Tamaulipas in northern Mexico—near the US border—, Reuters reported.

Authorities located the bodies inside and on the back of a burnt out pickup truck after travelling to the site, the Tamaulipas state prosecutor’s office said in a statement.

“Preliminary investigations point to the fact that the cause of death were shots from firearms, and that then the bodies were set on fire,” the statement said.

The area is known for “constant fights between rival criminal groups that traffic drugs, arms and migrants,” a source close to the investigation, who declined to be named, said.