In a separate incident Thursday, three human heads were found in three coolers in the town of Coyuca de Catalan, also in Guerrero, the provincial public security ministry said.

Two black bags and a blanket holding dismembered human body parts were found near the coolers. The authorities believe these may be the three bodies that correspond to the dismembered heads.

Armed groups linked to Mexico's drug cartels murdered around 1,500 people in 2006 and 2,700 people in 2007, with the 2008 death toll soaring to more than 6,000.

So far this year more than 4,450 people have died.