Mexican marines found 72 sticks of commercial synthetic explosives at a heavily armed camp in the southern state of Guerrero, the navy said Tuesday.

Such rural camps have frequently been used as training grounds and operating bases by Mexico's drug cartels.

The camp was found Monday near the border of Guerrero and neighboring Michoacan state, where drug gangs frequently operate.

In addition to explosives, marines found 14 rifles, eight grenades, more than 4,000 bullets and a small amount of marijuana at the camp, the navy said. No arrests were made.

Mexican cartels have begun using car bombs to attack police and other targets.

In the Guerrero state resort of Acapulco, where the Mexican Open tennis tournament is being held, police found the bodies of seven men, some mutilated, on Tuesday.

The hacked up remains of three men were found dumped in a highway tunnel that leads into Acapulco's tourist zone, state police reported. Some pieces of the bodies were missing.

Earlier, police found the bullet-ridden bodies of three men on Acapulco streets and discovered a fourth body half-buried and lacking its head.

Farther north, in the Pacific coast resort of Mazatlan, two men were shot to death in the parking lot of a hotel frequented by foreign tourists. Neither of the victims were tourists, but guests reported hearing the gunshots.

Drug cartel turf battles have killed more than 34,000 people since President Felipe Calderon launched a crackdown against drug traffickers in December 2006.

The government has sought to crack down on corrupt police who sometimes ally themselves with the cartels, and part of that effort focuses on vetting, identifying and tracking police officers.

The government announced Tuesday that it plans to include voice and DNA samples in a database of the nation's 620,000 police and public safety employees as a control measure. Criminals in Mexico sometimes masquerade as police.