"The cause of the crash is under investigation, however initial reporting indicates there was no enemy activity in the area at the time of the incident," ISAF said in a statement. The Pentagon said all five killed in the crash were Americans.
New US Defense Secretary Chuck Hagel left Afghanistan earlier on Monday after a difficult first trip to Kabul. His visit was marred by a suicide bomb attack near where he was holding a meeting, and differences with Afghan President Hamid Karzai, who accused the United States of colluding with the Taliban.
Helicopter crashes are not uncommon in Afghanistan and the Taliban and others often claim to have shot them down. Last August, 11 people, including seven US soldiers, were killed when a Black Hawk helicopter crashed in southern Afghanistan.
The worst such incident was in August 2011, when the Taliban shot down a CH-47 Chinook transport helicopter, killing all 38 people on board, including 25 US special operations troops.