(NewsNation) — The U.S. Army grounded its fleet of about 400 Chinook cargo helicopters after fuel leaks caused a “small number” of engine fires, the Army told NewsNation’s “Rush Hour” in an emailed statement Wednesday.

The helicopters have been the Army’s workhorse for six decades, which is why it was a decision made “out of an abundance of caution.”

Army spokeswoman Cynthia Smith also said the Army identified the cause of the leaks and is working to resolve the problem. In addition, she said some aircraft may not require the fix, so they may be able to return to flight soon.

The Army has identified the root cause of fuel leaks that caused a small number of engine fires among an isolated number of H-47 helicopters and is implementing corrective measures to resolve this issue. Based on the results of our investigation some aircraft may not require corrective measures and may soon return to normal flight operations. While no deaths or injuries occurred, the Army temporarily grounded the H-47 fleet out of an abundance of caution, until those corrective actions are complete. The safety of our Soldiers is the Army’s top priority, and we will ensure our aircraft remain safe and airworthy.

Cynthia Smith

Engine maker Honeywell told NewNation Wednesday they’ve narrowed down the problem to a part in the engine called an O-ring.

According to Honeywell, the Army replaced that part during maintenance with ones not meeting their specifications.

These cargo helicopters support combat and other critical operations, according to the Army. They can transport dozens of soldiers, loads of equipment and also play a role in missions including medical evacuations, search-and-rescues and parachute drops.

Should the choppers be out for a significant time, it could cause problems carrying out military opperations.

An private-sector engineer familiar with Chinooks told NewsNation’s “Rush Hour” Wednesday it’s a problem he hopes is solved quickly.

“With the functionality and the capability of them, I think everybody is all-hands-on-deck at this point to get these things in the air as fast as we can,” said Rob Roedts, senior director of aviation technology and manufacturing with Columbia Helicopters.

The Army said there are no other details on the engine fires, other than to say they have not caused injuries or deaths.

The issue also seems to be domestic problem; the Royal Canadian Air Force told NewsNation their Chinooks remain operational.