NATO troops shot at a speeding van on Wednesday in southern Afghanistan, killing two Afghan civilians and injuring a child, NATO officials said Thursday.

A van drove near a patrol of the NATO-led International Security Assistance Force at high speed in the Helmand province in south central Afghanistan and did not stop when troops gave hand signals to the driver to do so, according to ISAF officials.

The officials said the patrol then fired upon the vehicle and the two adult occupants inside were killed. Medical staff treated the injured and they were taken to nearby medical facilities.

ISAF officials said the incident will be investigated. They said they do not know why the vehicle failed to stop.

ISAF, a coalition of forces from about 37 countries, has a mandate from the United Nations to provide security and stability in Afghanistan to help the country rebuild itself after decades of war.