Mexican Attorney General Marisela Morales says 183 bodies have been uncovered so far from mass graves in the northeastern part of the country, near the U.S. border.
Morales made the comment Tuesday as she announced that 74 people, among them 17 police officers, have been arrested in connection with the investigation. The corpses were discovered recently around the community of San Fernando, in Tamaulipas, the state where 72 Central American migrants were found shot to death last August.
Authorities have linked Mexico's Zetas drug gang to these incidents. The Zetas started as a Mexican military unit that defected and began working with the Gulf cartel, based in Ciudad Juarez, Mexico, just across the border from El Paso, Texas. The Zetas split from the Gulf cartel last year. The two groups are now fierce rivals.
Elsewhere, investigators also have uncovered bodies from a mass grave in the northern state of Durango. They say that, to date, they have pulled the remains of 75 people from that site.
More than 35,000 people have been killed in Mexico's drug-related violence since the end of 2006, when President Felipe Calderon took office and ordered a crackdown on the country's drug cartels.
In a separate development, Mexican police Monday rescued 51 people, including 18 Central Americans and six Chinese, who were kidnapped in northeastern Mexico. Officials say 27 Mexicans were among those rescued.
Earlier this month, police freed 68 kidnapped people in Mexico's Reynosa area, across from McAllen, Texas. Authorities have taken four police officers into custody in connection with the abduction of the 68 individuals.
Some information for this report was provided by AFP and Reuters.