Authorities found the remains of 20 people distributed among eight clandestine graves while they were searching for two federal police who went missing earlier this month in the western state of Michoacan, sources in the Mexican Attorney General's Office told Efe.

Neither of the missing agents is among the dead, the sources said.

Some of the victims were bound and gagged and bore signs of torture, while most of them sported tattoos.

In the early hours Friday the cops announced they had found 16 bodies, but updated the number hours later after finding the remains of another four.

"A total of 20 bodies have been discovered up to now during the work of excavating the eight graves," the sources told Efe.

Authorities suspect the 20 bodies belong to "people who have some tie or relation" to gangland strife in Michoacan, one source said, referring to clashes between the rival Jalisco Nueva Generacion and Los Caballeros Templarios (Knights Templar) crime outfits.

Rene Rojas Marquez and Gabriel Quijadas Santiago, both investigators with the AG's office, went missing Nov. 3 while on assignment in Michoacan.

Superiors lost contact with the agents while the two men were traveling in an official vehicle, which was later found burned.

More than a score of municipal police officers and three civilians are in custody in connection with the disappearance of the federal investigators.

Based on the statements from the suspects, the AG's office believes Rojas and Quijano were arrested by corrupt cops who then handed them over to cartel gunmen.

The AG's office has doubled the size of the contingent looking for the kidnapped agents.

Michoacan is one of the states where the federal government is focusing its security operations because of the strong presence of drug traffickers. EFE