Mexican authorities say nine bodies have been found in a bloody pile in the border city of Nuevo Laredo, across from Laredo, Texas.
A Tamaulipas state official says the dead include five women and four men, and a hand-lettered sign was left atop the bodies in front of a house near a border bridge. Such signs are frequently left by drug cartels as messages to rivals.
The official was not authorized to be quoted by name and spoke on condition of anonymity.
The state prosecutors' office said in a statement it was investigating the killings Thursday.
Nuevo Laredo has long been dominated by the Zetas cartel, which has splintered into factions following the arrest or killing of top leaders.