The gruesome discovery of 43 men and six women in a highway ditch on the outskirts of San Juan on Sunday forced law enforcement authorities to close a section of the highway between Monterrey, capital of Nuevo Leon state, to the US border.

"To complicate the identification, none of these people were found with a head, and their (arms and legs) were mutilated," state security spokesperson Jorge Domene said. Some of the remains were found in plastic bags and many were naked.

Authorities said a few of the victims had tattoos of the Santa Muerte cult, a popular symbol among drug traffickers, and hoped that would assist them in identifying the bodies. Nuevo Leon state Attorney General Adrian de la Garza did not rule out the possibility the victims were US-bound migrants.

Domene said at a news conference that the bodies were accompanied by a note indicating the Zetas drug cartel taking responsibility for the massacre. Often discarding multiple bodies in public places is a warning to rival groups.

The victims could have been killed as long as two days ago at another location, then moved to San Juan, about 125 kilometers (75 miles) southwest of Roma, Texas. 

Controlling smuggling routes, the local drug market and extortion rackets has led to an increasingly bloody war being waged in the area in recent years.

This spate of murders is the third mass killing in nine days in the northern Mexican state. Twenty-three people were killed near the US border at the start of May, and last week authorities found 18 dismembered bodies in the state of Jalisco. 

In the lead up to the presidential and parliamentary vote on July 1, violence has been a key election campaign issue. 

jlw/rc (dpa, Reuters, AFP)