MONTERREY, Mexico -- A kicking, screaming teenager with a gunshot wound was found dangling from a rope over a busy highway Wednesday in the northern Mexico city of Monterrey. Police said another man alongside him was dead by the time rescuers arrived and a third was found dead below.

Witnesses told police a group of gunmen descended from a vehicle and hanged the men off a bridge around 10 a.m., stopping traffic along one of the busiest routes in Mexico's third-largest city, which has been plagued by drug-gang violence.

All three of the men had been shot and tortured, and their hands were bound with duct tape, according to a Nuevo Leon state police investigator who spoke on condition of anonymity because he was not authorized to discuss the case.

The dead man, estimated to be in his early 20s, dangled lifelessly in a blue shirt and plaid shorts. Bound in his hands was bound a cellphone, a possible sign that he was considered an informant.

Police said none of the victims had been identified.

Two other men, one with a foot cut off, were hanged by their necks from a pedestrian bridge Sunday in Monterrey. Both died.

The city has seen a spike of violence since the Gulf and Zeta cartels began fighting for control of drug traffic there two years ago.

In the Pacific resort of Acapulco, police unearthed the bodies of two women and eight men in a mass grave Wednesday, officials said. Acapulco also has been the scene of bloody cartel turf battles.

Omar Juarez Lozano, an Acapulco official, alerted police after smelling a foul odor in a vacant lot in a residential neighborhood. Police and soldiers dug and found the 10 bodies, put them in plastic bags and transported them to the city morgue in ambulances.

Police planned to do more digging at the site Thursday, officials said.

Also Wednesday, Mexican authorities said that two men wounded in any attack on a drug rehabilitation center in the northern city of Torreon died, raising the number of fatalities in the incident to 13.

Coahuila state prosecutors said in a statement issued Wednesday that two assailants stormed into the center Tuesday afternoon and opened fire. It was not yet clear what the motive for the attack was or which gang was responsible.

Drug cartels are known to use rehab centers to recruit addicts and rival gangs sometimes attack. Dozens of people have died in shootings at centers across Mexico. The worst incident left 19 people dead in Chihuahua city last summer.

More than 35,000 people have been killed in drug-related violence across Mexico since President Felipe Calderon launched an offensive against drug cartels when he took office in December 2006.