Authorities in western Mexico found the bound, tortured bodies of eight young men Thursday dumped on a roadside.
The men all appear to have been executed with a gunshot to the head, the attorney general's office in Michoacan state said in a statement.
The bodies, partly covered by bales of straw, and some half-clothed, were found near the border with Jalisco state. The victims appeared to be between 22 and 25 years of age, the statement said.
At least two were wearing women's underwear and had their fingernails painted, though the meaning of that was unclear. Drug cartels have been known to try to insult rivals by suggesting they are homosexuals.
Also Thursday, authorities said that another body has been pulled from a pit in the northwestern Mexican state of Sinaloa, bringing to 13 the number of corpses found there thus far.
Some of the bodies had apparently been in the pits for at least six months, said Sinaloa state Attorney General Marco Antonio Higuera Gomez.
The bodies are undergoing DNA tests and police are searching for the owners of the property where they were found by a farmer earlier this week.
Higuera Gomez said most of the bodies had a bullet hole to the head.
The discovery comes as authorities continue extracting bodies from mass graves in the northeastern state of Tamaulipas, where 122 corpses have surfaced so far. About 14 pits were found in the township of San Fernando, Tamaulipas, starting early this month.
The bodies of 70 of those victims — many of whom are believed to have been pulled off buses by members of the Zetas drug gang — arrived in Mexico City on Thursday for further genetic testing to confirm their identities.
A similar procedure was followed after the massacre of 72 migrants in San Fernando in August. Fourteen of those bodies — which have never been identified — were taken to a morgue in neighboring Mexico State to make room for the corpses from the latest massacre.
Authorities have not yet explained how cartel gunmen were able to get away with committing so many killings in the same township over the space of months, but it appears they may have received protection or help from corrupt local police.
Federal Attorney General Marisela Morales said Wednesday that 16 San Fernando police officers were detained for allegedly protecting members of the Zetas and covering up the kidnappings of bus passengers and others who traveled on a highway connecting San Fernando to the U.S. border.
The Mexican government said it is offering a 15 million-peso ($1.27 million) reward each for information leading to the arrest of Salvador Martinez Escobedo, the alleged leader of the Zetas in San Fernando, and Omar Estrada Luna, a cell leader. The government is also offering 10 million pesos ($846,000) for Roman Palomo Rincones and 5 million pesos ($423,000) for Sarai Diaz Arroyo, who both allegedly participated in the latest massacre, Morales said.
Another 17 suspects tied to the brutal Zetas gang were detained earlier in connection with the killings. Police said that some of them have confessed to abducting passengers from buses and killing them.
The motive for the bus abductions remains unclear, though prosecutors have suggested the gang may have been forcefully recruiting people to work for it.
And in the northern state of Sonora on Thursday, the army said in a statement that soldiers had arrested a top operator for the Sinaloa cartel at a hotel in the city of Hermosillo.
Raul Sabori is a suspect in the kidnapping and killing of two police officers in 2010 and the 2008 shooting death of Ivan Canastillo, a musician for the norteno musical group "Los Alazanes de Sonora."
Meanwhile, authorities in the border state of Ciudad Juarez said relatives have identified four bodies found buried in the desert as those of four men who were last seen when being detained by city police officers.
Arturo Sandoval, a spokesman for state prosecutors in Chihuahua, where Ciudad Juarez is located, said relatives recognized the bodies and the clothes they were wearing when they were detained March 26.
Three Ciudad Juarez police officers have been arrested in the case and face abuse of authority, forced disappearances, illegal use of public force and car robbery charges, Sandoval said.