At least 14 dismembered bodies were found in a truck abandoned in El Mante, a city in the northeastern Mexican state of Tamaulipas, authorities said.
The truck and its grisly cargo were found just after 2 p.m. Thursday, a Tamaulipas attorney general's office source told EFE.
Police decided to move the vehicle to another location to sort through the contents, but "initial reports are that there are 14 bodies", the attorney general's office source said.
A message was left with the bodies of the victims - 11 men and three women - but the contents have not been revealed.
El Mante, which is in a sugar-growing region, is about 140 km south of Ciudad Victoria, the capital of Tamaulipas, a state that has been rocked in recent weeks by a spike in drug-related violence.
Three people were wounded Wednesday when unidentified assailants threw grenades at two auto dealerships in Ciudad Victoria, state officials said.
The attacks targeted the Renault and Volkswagen dealerships in the state capital.
Police found the bodies of 23 people May 4 in Nuevo Laredo, located across the Rio Grande from Laredo, Texas, with 14 of the victims mutilated and nine left hanging from a bridge.
Tamaulipas and neighbouring Nuevo Leon state have been rocked by a wave of violence unleashed by drug traffickers battling for control of smuggling routes into the US.
The army is carrying out "operation northeast" in Tamaulipas, Nuevo Leon, Coahuila and San Luis Potosi states in an effort to weaken the drug cartels that operate in the region.
The Gulf drug cartel and Los Zetas, a band of army special forces deserters turned hired guns and drug traffickers, are blamed for the violence.