Soldiers opened fire on a family's car at a checkpoint in northern Mexico, killing a 15-year-old boy and another person, authorities said.
It was at least the second time this year that a family has been caught up in a shooting involving Mexico's military, which has come under intense criticism for human rights abuses as soldiers fight brutal drug cartels.
Soldiers apparently shot at the car when the driver failed to stop at the checkpoint Sunday on the highway from the northeastern city of Monterrey to Laredo, Texas, said Javier Trevina, Nuevo Leon state government secretary.
A 15-year-old boy and a man were killed, he said. Three other adults and two children were wounded.
The Defence department promised an investigation, expressing its "deep condolences to the family" in a statement on Monday.
The military is mired in a controversy involving the April death of two brothers, ages 5 and 9, on a highway in Tamaulipas, a state bordering Nuevo Leon.
The National Human Rights Commission accused soldiers of shooting the children and altering the crime scene to try to blame the deaths on drug cartel gunmen.
The army denies the allegations and says the boys were killed in the crossfire of a shootout between soldiers and gunmen.
The scandal has renewed demands from activists that civilian authorities, not the army, investigate human rights cases involving the military.
More recently, soldiers killed a US citizen on August 22 outside the Pacific coast resort city of Acapulco.
In a statement to police, an army lieutenant claimed that Joseph Proctor, who had lived Mexico for several years, shot first at the military convoy on a highway between Acapulco and Zihuatanejo.
The Defence Department said it was investigating the officer's claim, which Proctor's father, William Proctor, said he found hard to believe.