A Mexican police spokesman confirms the discovery of the decapitated bodies of 49 people on a road Reuters

Forty-nine decapitated and mutilated bodies were found on Sunday dumped on a highway connecting the northern Mexican metropolis of Monterrey to the US border, in the latest suspected outburst in an escalating war among drug gangs.

Mexico's organized crime groups often abandon multiple bodies in public places as warnings to their rivals, though Nuevo Leon state attorney general Adrian de la Garza said he did not rule out the possibility that the victims were US-bound migrants.

The bodies of the 43 men and six women were found in the town of San Juan on the non-toll highway to the border city of Reynosa at about 4am on Sunday morning, 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 75 miles south-west of the border crossing at Roma, Texas.

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.

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 183 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.