Authorities said Saturday that police had unearthed at least 51 bodies from a mass grave outside Monterrey, Mexico's business capital.

Excavation continued at the trash dump-turned mass grave which was feared to be the country's largest clandestine body dumping ground in drug wars.

The digging started on a tip from an informant and investigators soon uncovered the bodies.

Alejandro Garza y Garza, attorney general of Nuevo Leon state where Monterrey is located, said the bodies included 48 men and three women.

Investigators are identifying the bodies.

"The majority of these bodies have tattoos of different types that could give us an indication about whether they belonged to one group or another (drug cartel)," said the state attorney general.

Some of the victims from the mass grave were believed to have died as recently as two weeks ago, police sources said.

"This is the level of violence we expect when these groups clash," State Governor Rodrigo Medina said.

Drug-related violence has claimed more than 25,000 lives in Mexico since incumbent Mexican President Felipe Calderon launched the country's anti-drug campaign in late 2006.

In the past, victims of drug-related violence were mostly gang members, but cartels have also killed law enforcement officials lately, officials said.