Police in the popular Mexican beach resort of Cancun found the bodies of 12 people on Friday with signs they were tortured and killed by drug gang members.
Police recovered the bodies of nine men and three women from graves in an area less than 2 miles (3 km) from Cancun, a tourist destination increasingly drawn into Mexico's drug war, and said more corpses might be found.
"They died of suffocation. They were found with their hands and feet tied and with signs of torture. At least three were cut post-mortem on their chests with the letter Z," said Quintana Roo state government official Francisco Alor.
The letter "Z" is a symbol in Mexico of the Zetas drug gang, the former armed wing of the powerful Gulf cartel.
President Felipe Calderon launched a military crackdown on the drug cartels in late 2006, sparking turf wars and attacks on police. More than 25,000 people have since been killed across Mexico, many of them tortured, beheaded or strung from bridges. June is on pace to be among the bloodiest months yet.
Earlier this month, police found six bodies in a cave near Cancun, also with "Z" carved in their chests.
In May, the mayor of Cancun was arrested on money- laundering and drug-related charges, making him one of the highest-ranking officials swept up in Mexico's crackdown on narcotics trafficking.
Cancun, a city of more than 500,000 people, attracts millions of US and European tourists annually with its Caribbean beaches and proximity to Mayan ruins on the Yucatan Peninsula.