The dismembered remains of 14 men were found on Tuesday stuffed inside a minivan left near the town hall of a Mexican city on the US border that is often a flashpoint for the country's drug war, officials said.
The remains were found in downtown Nuevo Laredo just after sunrise packed inside 10 black plastic bags found in the vehicle, the officials said.
A threatening message was found with the bodies.
Nuevo Laredo, adjacent to the south Texas city of Laredo, is a stronghold for the Mexican drug cartel the Zetas.
More than 50,000 people have been killed since President Felipe Calderon began a campaign to curb drug trafficking in 2006.
Much of that violence has been focused on border towns that serve as transit points for illicit drugs.