The number of bodies found in 16 clandestine graves in western Mexico has risen to 31, including the body of a woman.
Many of the bodies have been found bound or gagged.
Some showed signs of having been tortured, according to a federal prosecutors official who spoke on Friday on condition of anonymity because he is not authorized to talk to the press.
The graves are in La Barca, in a remote area by Lake Chapala, which is popular among tourists and American retirees.
Local police officers who confessed to working with a drug cartel led agents to the mass graves last week near the border between Jalisco and Michoacan states.
The area is the site of a turf war between the Knights Templar and the New Generation cartels.