A helicopter contracted by the NATO-led force in Afghanistan crashed in southern Helmand province Tuesday, killing six civilians, an official said. Two U.S. Marines died in the same region, the Associated Press reported. The white helicopter crashed and caught fire around daybreak in Sangin district, said Fazel Haq, the top district official. Six civilians on board were killed and an Afghan national on the ground was injured, said a spokesman for the NATO-led force. Authorities were investigating the cause of the crash, he said. The nationalities of those killed were unknown.