Mexican authorities have officially confirmed through DNA testing that three U.S. citizens were among the four bodies found shot to death near the border more than two weeks after they went missing.

The statement issued late Friday by the Tamaulipas state prosecutor's office did not mention the fourth body, which is thought to be the Mexican boyfriend of one of the dead Americans.

The Mexican father of the three Americans had previously identified his children from photos of the bodies found near the border city of Matamoros.

Tamaulipas officials say they are investigating a possible police connection to the deaths. The family of the Americans has said witnesses reported they were taken away by armed men who identified themselves as part of the "Hercules" tactical security unit in Matamoros