MEXICO CITY -- A Mexican official says police found the decapitated bodies and heads of four men in downtown Nuevo Laredo, a city across Laredo, Texas.

The Nuevo Laredo city official who spoke on condition of anonymity because he is not allowed to speak about the case says the bodies were dumped Friday night at a monument in the city's center.

The official said Saturday that police also found a threatening message directed to the Gulf drug cartel.

Nuevo Laredo is in Tamaulipas state, where the Gulf cartel and the Zetas have been battling for lucrative drug routes into the United States.