The decapitated bodies of seven men have been found on a rural road in an area where several drug cartels operate. The victims - all men - were between 22- and 49-years-old.
The victims "were all decapitated, placed on a little-traveled dirt road," Martin Robles, deputy attorney general for northwestern Sinaloa state where the murders took place, told reporters.
The bodies were found near the town of Rosario, located about 60 miles (100 kilometers) south of the Pacific resort of Mazatlan, he added. The area is quite close to the home turf of jailed drug lord Joaquin "El Chapo" Guzman, but it was not immediately clear if Guzman's notorious cartel was involved in the killings.
Robles said the attack could have been carried out in response to the deployment of troops in the area earlier in the month or because the men crossed into gang territory. He added that the victims were all loggers who did not have criminal records. They had been missing since June 13.
In recent years, Sinaloa state has seen bouts of violence between the army and drug traffickers. But such gruesome displays of crime have been rare despite longstanding rivalries between two drug and criminal gangs.
Elsewhere in Sinaloa, around 150 families fled three villages in the remote mountain region where Guzman was born, the mayor of the municipality of Badiraguato said. They left because of "possible clashes" between armed groups that recently arrived in the area.
The families were living in Arroyo Seco, La Palma and La Tuna, where Guzman's elderly mother still lives. Guzman was recaptured in Sinaloa in January, six months after he escaped prison. He is currently being held at a jail near the US border, where he is awaiting extradition to the United States to face drug trafficking, money laundering and murder charges.
Robles said there were no clashes in the area or attacks against residents. But he confirmed that three men had been found dead.
Mexico has also been investigating the disappearance of 43 trainee teachers after they took part in a protest in the southwestern city of Iguala, in Guerrero state, in September 2014. It's believed they were murdered and their bodies burned.