Police have found the severed heads of three men in a cooler left on the side of a highway in southern Mexico. Their bodies were found in a taxi about a mile away.

The Public Safety Department in the Pacific coast state of Guerrero says the discovery was made Monday near the resort of Zihuatanejo. The plastic foam cooler was wrapped in tape and a message was attached, but police did not reveal what it said.

Some of the bodies found inside the abandoned taxi had their hands bound behind their backs, and they showed signs of torture.

Mexican cartels frequently mutilate or decapitate their victims as part of drug violence has killed more than 10,750 in the last 2 1/2 years.