Forty-nine decapitated and mutilated bodies have been found dumped on a highway connecting the northern Mexican metropolis of Monterrey to the U.S. border in what appears to be the latest blow in an escalating war of intimidation among drug gangs.

Mexico's organized crime groups often abandon multiple bodies in public places as warnings to their rivals, and authorities said at least a few of the recent victims had tattoos of the Santa Muerte cult popular among drug traffickers. But Nuevo Leon state Attorney General Adrian de la Garza said he did not rule out the possibility that the victims were U.S.-bound migrants. 

The bodies of the 43 men and six women were found Sunday in the town of San Juan on the non-toll highway to the border city of Reynosa at about 4 a.m. local time, forcing police and troops to close off the highway.

Nuevo Leon state security spokesman Jorge Domene said at a news conference that a banner left at the site bore a message with the Zetas drug cartel taking responsibility for the massacre.

Domene said the fact the bodies were found with the heads, hands and feet cut off will make identification difficult. The bodies were being taken to Monterrey for DNA tests.

De la Garza said the victims could have been killed as long as two days ago at another location, then transported to San Juan, a town in Cadereyta municipality, about 175 kilometres west-southwest of McAllen, Texas, or 125 kilometres southwest of the Roma, Texas, border crossing.

Competition intensifying among rival cartels 

Mexican drug cartels have been waging an increasingly bloody war to control smuggling routes, the local drug market and extortion rackets, including shakedowns of migrants seeking to reach the United States.

Luis Horacio Najera, a Mexican journalist exiled in Canada, suspects the Zetas cartel was responsible early on in the investigation. The tattoos on the victims’ bodies are common among the rival Gulf cartel.

"The message is we are [in] control of these territories," Najera told CBC News.

"There’s a huge competition for the drugs market," he added, explaining that there are about 10 criminal organizations operating in Mexico, up from six or seven at the beginning of President Felipe Calderon’s administration.

Increased significance

Najera, who fled from Ciudad Juarez when his family was threatened, said such displays of violence have increased significance in the lead up to an election.

"The criminals are trying to put some more pressure on the government, plus politicians, plus society," he said.

A drug gang allied with the Sinaloa cartel left 35 bodies at a freeway overpass in the city of Veracruz in September, and police found 32 other bodies, apparently killed by the same gang, a few days after that.

The goal apparently was to take over territory that had been dominated by the Zetas. Twenty-six bodies were found in November in Guadalajara, another territory being disputed by the Zetas and the Sinaloa group.

So far this month, 23 bodies were found dumped or hanging in the city of Nuevo Laredo and 18 were found along a highway south of Guadalajara, Mexico's second-largest city. 

In April, police found the mutilated bodies of 14 men in a minivan abandoned in downtown Nuevo Laredo, along with a message from an undisclosed drug gang. Also in April, the tortured and bound bodies of seven men were dumped in the Pacific port city of Lazaro Cardenas along with messages signed by allies of the Sinaloa drug gang.

Officials last year found 193 bodies in mass graves in the Tamaulipas state town of San Fernando. They were believed to have been migrants killed by the Zetas drug cartel.

Another 72 migrants, many of them from Central America, were found slain in San Fernando in 2010.

With files from CBC News