Police in the northwestern state of Sinaloa, the birthplace of Joaquin "El Chapo" Guzman and other powerful drug traffickers, found 13 bullet-riddled bodies inside two vehicles, prosecutors said.
The bodies of the victims, including four women, were discovered on Saturday, Sinaloa Attorney General's Office media relations director Guadalupe Martinez told EFE.
The grisly find was made by police in Tepeguaje, a community outside the city of San Ignacio, which is in the border region with Durango state.
A boy, who was not injured, was with the bodies of the unidentified victims, Martinez said.
Police sealed off Tepeguaje, which is in a mountainous area at the center of a turf war among rival drug gangs for control of smuggling routes into the United States.
Sinaloa is home to the powerful drug cartel that bears the state's name.
The Sinaloa organization, sometimes referred to by Mexican officials as the Pacific cartel, is the oldest drug cartel in Mexico and has large smuggling and distribution networks in South America, the United States and Europe.
Joaquin "El Chapo" Guzman was captured on Jan. 8 in Los Mochis, a Pacific coast city in Sinaloa.