Criminal investigators in northern Mexico say a suspect has been arrested and is under investigation for possible connections with the deaths of nine U.S. citizens — three women and six children — slaughtered Monday when cartel gunmen ambushed their vehicles.

In a statement posted on Facebook, the Agency for Criminal Investigation for the state of Sonora said Tuesday that the suspect was found in the town of Agua Prieta, right at the border with the U.S. state of Arizona, holding two hostages who were gagged and tied inside a vehicle.

The suspect, whose gender was not specified in the release, was also found in the possession of four assault rifles and ammunition, as well as various large vehicles including a bullet-proofed SUV.

Officials have said that the gunmen may have mistaken the group's large SUVs for those of a rival gang amid a vicious turf war. Eight children, some just infants, survived the ambush.