Kabul, Afghanistan (CNN) -- Nine American service members died in a helicopter crash Tuesday in southern Afghanistan, where an international coalition has stepped up efforts against the Taliban, according to a Western defense source.
The source spoke on condition of anonymity when revealing the nationalities of the nine, who've added to the grim toll for Operation Enduring Freedom.
According to a CNN tally last updated Monday, 517 coalition troops had been killed in Afghanistan this year, including 341 Americans.
Even without the inclusion of the latest numbers, the figures make 2010 the deadliest year for Operation Enduring Freedom since it began nine years ago.
The International Security Assistance Force, as the coalition is known, did not release the nationalities of Tuesday's crash victims.
Two other service members, along with an Afghan National Army soldier and an American civilian, sustained injuries in the crash. They were taken to a NATO medical facility.
ISAF has ruled out enemy involvement in the crash, said Jan Rasuli, spokesman for Zabul Province's governor, Mohammad Jan Rasuli.
CNN
