Mexican police on Friday found four bodies hanging from a bridge in the northern city of Saltillo, Coahuila state's security spokesman told Efe.

The four bodies bearing signs of tortute and wrapped in bandages had been hung from the El Sarape bridge, which links Saltillo's east side with the city center, Sergio Sibeles said.

Personnel from the military and various police forces were dispatched to the scene.

After the arrival of forensics personnel from the Coahuila state Attorney General's Office, the bodies were taken to a coroner's office for an autopsy.

A threatening message believed to have been left by an organized crime gang was found at the scene, local media reported. Its content was not revealed.

Authorities, meanwhile, posted messages on social-networking sites urging local residents to stay away from the area during the crime-scene investigation.

Saltillo has been the scene of turf battles in recent years pitting the Los Zetas, Gulf and Sinaloa cartels. Army soldiers and federal police have been deployed to the city in an effort to stanch the violence. EFE