The severed heads of six men have been found in a black plastic bag on top of a car in southern Mexico.
Six headless bodies were also discovered within the vehicle on Monday (local time) in Chilpancingo, the state capital of Guerrero.
Security spokesperson Roberto Alvarez says four more bodies were found in the nearby township of Chilapa.
All of the bodies found in Chilapa showed signs of torture, while two of them had been found shot to death on a highway.
It's not thought the two incidents in Chilapa and Chilpancingo were related.
Guerrero has the highest homicide rate of Mexico's states, and is one of the poorest parts of the country.