Two bodies were found hanging from a bridge on the free road from Tijuana to Rosarito early Monday morning.

Two bodies were found hanging from a bridge on the free road from Tijuana to Rosarito early Monday morning. Tijuana authorities also report four young men dead in a separate case, in a working class neighborhood many miles from downtown Tijuana.

Baja Calfiornia's Attorney General's office says the bodies were hung by their feet and both men were decapitated. Investigators say the men were both 22 years-olds from Rosarito

Police found the heads in a pick-up truck parked on the bridge. One of the heads, authorities say, was covered with baby clothes. Police also found a message from the killers, often characteristic of drug cartel hits, on the truck's windshield.

Investigators say one of the men has a prior charge for property damage, the other for carrying a restricted firearm.

The hanging bears the hallmarks of drug trafficking organizations. Though, Mexican authorities would not comment on this case.

About six hours earlier, on Sunday evening, police discovered four men between the ages of 18 and 22 shot to death on the patio of a home in a neighborhood called Infonavit Latinos. Baja California's Attorney General's office specualtes drug dealing may have motivated the killings. Though, they say only two of the men have criminal records and do not hypothesize as to why they were killed.

Authorities say 21 year-old Angel Cruz Valdobino, one of the dead, was arrested and deported two years ago for selling crystal in Los Angeles. They say he was also jailed for a year in the US, two or three years ago, after US police caught him smuggling cash from the US to Mexico.

Mexican investigators theorize gunmen could have killed the four men because Cruz failed to turn over drug money he'd smuggled from the US. Investigators also speculate Cruz may have been selling drugs out of the house where he and the others were killed, and that another of the men may have delivered the drugs to clients by taxi. Cruz allegedly had four taxis. Authorities say mobile drug sales using taxis is a recent trend in Tijuana.

A dozen bullet casings found at the scene are the kind of ammunition AK47's use. That's one of drug cartels' favored guns. Authorities tied a 9mm gun used in the murders to two previous murder scenes. Two of those three victims allegedly sold drugs.

Tijuana has made progress in controlling drug violence recently. Shootouts in public places and the public display of corpses have tapered off. Though drug murders grind on in the city's outskirts.

Just a few days ago, Mexico's President touted Tijuana as a success in his four year old drug war.

His remarks came as he kicked off a two week long, $5 million conference to try to regain respect for Tijuana and show off the city to the world.

Almost exactly a year ago, on October 9th, a Baja California employee, Rogelio Sanchez, who was in charge of drivers licenses, was found mutilated and hung from a bridge, also on the highway between Tijuana and Rosarito. He had been kidnapped a few days earlier. At the time, a spokeswoman with Baja California's Attorney General's office said Sanchez gave licenses to members of organized crime groups.