A U.S. helicopter that crashed a week ago northwest of Baghdad was shot down, the U.S. military said on Wednesday.

"Initial evidence indicated that the CH-46 Sea Knight helicopter went down as a result of mechanical failure," Major Jeff Pool, a spokesman for the Multi National Force - West, said in a statement.

"After further investigation using all available means, the cause of the incident has been confirmed to be hostile fire," Pool said.

On Feb. 7, a marine CH-46 helicopter, also known Chinook, went down northwest of Baghdad, killing seven people aboard, including the crew.

Witnesses in the area west of the U.S. airbase of Taji, 20 km north of Baghdad, said that they saw a helicopter crashed after it was hit by ground gunfire.

Source: Xinhua