PARIS -- French police say a single weapon was used to kill four people in the Alps, and investigators are again scouring the scene of the crime.

A police official said Tuesday that a handgun was used to kill a British-Iraqi couple, a French cyclist and another woman. The official, who was not allowed to speak publicly about the investigation, did not provide the caliber of the weapon.

Investigators have at last confirmed the identity of the other victim, according to the Sipa news agency. The agency reports she is the Swedish-Iraqi mother-in-law of the car's driver, Saad al-Hilli, and grandmother to two girls who survived the attack.

The 4-year-old girl couldn't tell investigators what happened. Police plan to question her seriously injured 7-year-old sister.

The reason for the killings remains unclear.

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  • Crime coordinator Capt. Laurent Dourel, left, Annecy prosecutor Eric Maillaud, second left, and French Gendarmes Col. Bertrand Francois, third left, and Lt. Col. Benoit Vinneman atttend a news conference in Annecy, French Alps, on Thursday, Sept. 6, 2012. (AP Photo/Lionel Cironneau)

  • Annecy prosecutor Eric Maillaud answers a question during a news conference in Annecy, France, on Thursday, Sept. 6, 2012. (AP Photo/Lionel Cironneau)

  • A gendarme blocks access to the site where people were shot to death near Chevaline, French Alps, on Thursday, Sept. 6, 2012. (AP Photo/Laurent Cipriani)

  • A Gendarme's car heads to a killing site near Chevaline, the French Alps, on Wednesday, Sept.5, 2012. (AP Photo/Alexis Moro)

  • Gendarmerie Col. François, left, and Annecy prosecutor Eric Maillaud answer reporter near a killing site, near Chevaline, the French Alps, on Wednesday, Sept. 5, 2012. (AP Photo/Alexis Moro)

  • Gendarmes block access to a killing site near Chevaline, the French Alps, on Wednesday, Sept. 5, 2012. (AP Photo/Alexis Moro)

  • Gendarmes blocks access to site where people were shot to death near Chevaline, the French Alps, on Thursday, Sept. 6, 2012. (AP Photo/Laurent Cipriani)