The burnt bodies of 19 people have been found close to the Mexican border with the US, according to officials from Tamaulipas state.
Police found two burnt-out vehicles on Saturday and initial findings indicate the people were shot and then set alight. Violent drug gangs operate in the area, where migrants also try to cross the border into Texas.
An official said the victims may be undocumented migrants, reports AFP.
The north-eastern state of Tamaulipas is known for violent killings and disappearances, often linked to powerful drug cartels who battle for territory. The Mexican government is fighting what it calls a war on drugs, and its security forces have previously been accused of detaining suspects who later go missing.