Forensic technicians work at a crime scene in the municipality of Cadereyta May 13, 2012. [Photo/Agencies]

CADEREYTA JIMENEZ, Mexico - Suspected drug gang killers dumped 49 headless bodies on a highway near Mexico's northern city of Monterrey in one of the country's worst atrocities in recent years.

The mutilated corpses of 43 men and 6 women, whose hands and feet had also been cut off, were found in a pile on a highway in the municipality of Cadereyta Jimenez in the early hours of Sunday, officials from the state of Nuevo Leon said.

"What's complicating the identification of all the people was that they were all headless," said Jorge Domene, the Nuevo Leon government's spokesman for public security, who said the other body parts were missing.

Domene said the brutal Zetas drug gang claimed responsibility for the murders in a message found at the scene.  

The massacre was the latest in a string of mass slayings that have convulsed Mexico in recent months, many of them in the north of the country, where the Zetas have waged a war against rival groups for control of smuggling routes.

The Zetas gang was founded by deserters from the Mexican army who became enforcers for the Gulf cartel, which once dominated the drug trade in northeastern Mexico. Leaders of the Zetas later split from their employers and the two gangs have since fought for control of trafficking routes.  

The Zetas have also been at war with the powerful Sinaloa cartel on the other side of the country.

President Felipe Calderon has staked his reputation on bringing Mexico's drug gangs to heel, sending in the army to fight them shortly after taking office in December 2006.

Since then, however, the violence has spiraled, and more than 50,000 people have fallen victim to the conflict.

The violence has eroded support for Calderon's conservative National Action Party (PAN), which looks likely to lose power in presidential elections on July 1.  

Mexican security analyst Alberto Islas said the latest bloodbath was a sign the federal and state governments were failing to get the upper hand.

"They're fighting across the whole country with complete impunity," he said. "The government has to send out a very clear signal they will stop the violence and find those responsible."

TATTOOED VICTIMS

The headless victims have not been identified.

The bodies showed signs of decay that indicated they may have been dead for days, de la Garza said. He also said there had been no mass disappearances reported in the state, suggesting the victims could have been killed somewhere else.

De la Garza said many of the bodies were tattooed, which could offer a clue to their identities.

Nuevo Leon Attorney General Adrian de la Garza said the corpses could be of migrants passing through Mexico to the United States. Migrants have been targeted by criminal gangs in the past.

Violent street gangs in Central America such as the Maras have distinctive tattoos, though security spokesman Domene said the victims did not show these markings.

Domene said some had tattoos of Santa Muerte, or "Holy Death" a female skeletal grim reaper venerated by both gangs and some broader, non-criminal sections of Mexican society.   The corpses were taken to Monterrey and authorities said they would perform DNA tests. Thousands of Mexico's drug war victims have never been identified.

SPIRAL OF VIOLENCE

The bloody killings in Nuevo Leon were the worst there since 52 people died in an arson attack on a casino in Monterrey in August. That attack was also blamed on the Zetas.

Monterrey is Mexico's richest city and was long seen as a model of economic development, but it has been ravaged by the drug war over the last three years.

There has been an escalation of gruesome mass killings in Mexico in recent weeks.

Last Wednesday, 18 people who were found decapitated and dismembered near Mexico's second-largest city, Guadalajara.

A week earlier, the bodies of nine people were found hanging from a bridge and 14 others found dismembered in the city of Nuevo Laredo, just across the U.S. border from Laredo in Texas.

Late last year, several mass killings took place in the eastern state of Veracruz, which has been ravaged by the Zetas.