The Tamaulipas state prosecutor's office said 11 people had been arrested and another five kidnapping victims had been set free in the same operation on Wednesday.

Police and military staff learned on March 25 that several buses had disappeared in the area, leading to their investigation which turned up a grisly find: eight mass graves in the La Joya farming village, in the town of San Fernando, the prosecutor's office said.

"With our work that is underway, we are trying to establish if the remains are those of the people who went missing on the buses," the prosecutor's statement said.

Authorities said they feared the number of dead would rise as the remains had only been counted in three of eight mass graves. A military patrol located the mass grave, the source added.

AFP