At least 59 bodies have been found in mass graves in northern Mexico, close to the U.S. border, near where 72 migrant workers died in a suspected drug gang massacre last year.
The bodies, including 43 corpses piled into one grave, were found by officials Tamaulipas state who were investigating the March 25 abduction of one or more busloads of passengers.
"With our work that is under way, we are trying to establish if the remains are those of the people who went missing on the buses," the Tamaulipas state prosecutor said in a statement.
Officials said the death toll could rise. They had only counted the bodies in three of eight mass graves, AFP said.
The prosecutor said investigations had so far resulted in 11 arrests and the rescue of five people held captive.
Tamaulipas Gov. Egidio Torre Cantu "energetically condemned" the crimes, the LA Times reported.
The discovery of the bodies late Tuesday was made in San Fernando, the same rural town — 90 miles from the Texas border — where 72 South American migrants were killed last August.
Authorities said the Zetas gang, one of several major drug trafficking outfits operating in Mexico, carried out the killings after the migrants refused to work for them, AP said.
Thousands of angry citizens took to the streets of 38 Mexican cities on Wednesday to protest escalating drug violence that has killed more than 34,600 people since December 2006, according to AFP.
A military crackdown on drug gangs launched by Mexican President Felipe Caldero's government in the same year has so far failed to arrest the bloodshed.
Read more on Mexico's drug wars on the GlobalPost special report: 7 Circles of Juarez