Mexican authorities found seven human heads on a street in a town in the northern state of Durango Thursday, but did not immediately find the bodies.
"The discovery was reported at around 6:00 am (1200 GMT). Seven human heads were found on a street in Santiago Papasquiaro," said Raymundo Enriquez, spokesman for the Durango attorney general's office.
The heads were found in a residential area of the town of 40,000 people, some 750 miles (1,200 kilometers) northwest of Mexico City, along with messages attributed to crime gangs which threatened a local justice official, he said.
Parts of Mexico, including Durango, are gripped by gangland-style violence in which brutal killings such as beheadings are used to send messages to rivals.
Shootouts and mass graves have been reported in the area of the latest killings, also known for illegal marijuana fields and a strong presence of the Sinaloa drug gang of Mexico's most-wanted fugitive, Joaquin ‘El Chapo’ Guzman.
Some 50,000 people are believed to have died in drug gang-related violence since December 2006, when President Felipe Calderon started a military crackdown on organized crime with tens of thousands of troops.