"They were conducting an extraction of soldiers. It took place, and shortly after the extraction was when the mechanical malfunction occurred," Task Force Lightning spokesman Lt. Col. Mike Donnelly said.

He said the Kirkuk area is a combination of rolling hills and flat desert plains. There was an established landing zone for the operation.

Task Force Lightning is headquartered in Tikrit at Contingency Operations Base Speicher and has responsibility for 23,000 soldiers in several units over a wide area north of Baghdad.

The aircraft has been recovered, and the identities of the victims and their unit information will not be released until their families have been notified, the Air Force Times reported on its Web site.

The four crew members and 10 passengers killed near Kirkuk were part of a two-aircraft formation carrying out a night operation with several different elements on the ground and in the air.

The human toll in today's crash is the deadliest for the Army this year. On Jan. 20, 12 soldiers were killed in Diyala Province north of Baghdad when their helicopter was shot down by a missile believed to have been fired from the back of a pickup truck.