Seven decapitated bodies were found Thursday in the central Mexican town of Jojutla, authorities said.
The bodies were inside a pick-up truck abandoned next to a gas station, while the severed heads were left nearby, the Morelos state Attorney General's (AG) Office said.
Police made the gruesome discovery after receiving an anonymous telephone tip, the AG's office said, adding that the truck had been reported stolen.
Authorities have yet to identify any of the victims and autopsies will be required to determine the cause of death.
Morelos, just south of Mexico City, has been battered in recent months by gangland violence and the national government recently dispatched additional federal police and army troops to the state.
Conflict among rival cartels and between criminals and the security forces has claimed more than 50,000 lives in Mexico since December 2006, when newly inaugurated President Felipe Calderon - whose term ends in December - militarized the struggle against drug trafficking.