WASHINGTON (AP) — The Army said Tuesday it has grounded its fleet of about 400 Chinook cargo helicopters after fuel leaks caused a “small number” of engine fires.

Army spokeswoman Cynthia Smith said the Army has identified the cause of the leaks and is working to resolve the problem. Smith said that some aircraft may not requires the fix, so they may be able to return to flight soon.

The fleet was grounded during the past weekend. Smith said there were no injuries or deaths associated with the fires but the Army temporarily grounded the fleet out of an abundance of caution.

The Chinook is the Army’s key heavy-lift helicopter, used to transport troops and equipment, and was a familiar sight in the Afghanistan and Iraq wars.