Forty-nine bodies, at least some of them mutilated, have been found dumped on a motorway connecting the northern Mexican city of Monterrey to the US border, officials said.
A law enforcement official said the bodies of 43 men and six women were found in the town of San Juan on the non-toll motorway to the border city of Reynosa at about 4am (0900 GMT), but officials were still investigating.
Authorities closed off the motorway, blocking the way for hundreds of motorists, as federal and state police, joined by Mexican troops, sealed off the scene.
The discovery echoes several other recent cases in which drug gangs have left bodies scattered in public places as warnings to rivals.
Thirty-five bodies were left at a motorway overpass in the city of Veracruz in September. Twenty-six were found in November in Guadalajara.
So far this month, 23 bodies were found dumped or hanging in the city of Nuevo Laredo and 18 were found along a motorway south of Guadalajara.