Accetta said a US military investigation team was on its way but had not yet arrived in Afghanistan.
Coalition soldiers were still at the crash site, which residents said was not far from the Kabul to Kandahar highway.
Acetta said: "We do still have the crash site secured. We will not leave the crash site unsecured for the safety of the locals and during the investigation."
The coalition advised Afghans to stay away from the area on Sunday for their own safety, saying "recent reporting indicated a Taliban build-up for operations against the coalition forces in the region."
The investigation will try to determine "exactly what caused the power loss," said Sharon Engelneier a captain and coalition media officer.
The crash was the first this year although there have been a string of similar ones involving foreign forces deployed to Afghanistan.
Most of the crashes have been accidents although in June 2005 a US Chinook was shot down by a rocket-propelled grenade in the eastern province of Kunar, killing all 16 servicemen on board.