Police find 13 bodies shot dead in western Mexico

Blankets cover the bodies of dead men on a street in Zitacuaro in the state of Michoacan January 9, 2012.

MEXICO CITY (Reuters) - Police found thirteen semi-naked bodies piled one atop the other outside a convenience store in western Mexico on Monday, local authorities said.

The bodies, which were found along with threatening messages, had been shot in what appeared to be a flare-up in an ongoing turf war between drug cartels in Michoacan state.

All 13 victims were male and found at the store off a highway on the outskirts of Zitacuaro, 100 miles west of Mexico City, the state attorney general's office said. Local emergency services said the bodies, three of which were minors, showed signs of decomposition, suggesting they were killed days earlier and then dumped outside the store in the early morning hours.

Michoacan, the home state of President Felipe Calderon, has been relatively calm since police killed the top boss of the cult-like La Familia cartel in December 2010.

The state had been plagued with violence as rival gangs fought over lucrative methamphetamine trafficking routes and marijuana fields across western Mexico.

More than 46,000 people have died in drug-related violence since Calderon launched an army-led crackdown on the cartels after taking office five years ago.

Zitacuaro is a city used by tourists as a launching point to visit nearby butterfly sanctuaries during the annual monarch migration in October and November.

(Reporting by Julie Gordon and Lizbeth Diaz; Editing by Doina Chiacu)