- The US Army had grounded its entire fleet of CH-47 Chinook helicopters, per The Wall Street Journal.
- The Army confirmed it was aware of a small number of engine fires in the Boeing-made helicopters.
The US Army has grounded about 400 Boeing-made CH-47 Chinook helicopters due to concerns over engine fires.
The Wall Street Journal first reported the news.
US Army officials told the newspaper that the entire fleet of Chinook helicopters had been grounded after they were made aware of a small number of engine fires.
An Army spokesperson told The Journal that fuel leaks had been found to cause "a small number of engine fires among an isolated number" of aircraft.
There had been no injuries due to the fires and the fleet had been grounded "out of an abundance of caution," officials said.
The US Department of Defense did not immediately respond to Insider's request for comment.
The Army is looking specifically at engines manufactured by Honeywell International, sources told The Journal.
Honeywell said in a statement it had found some O-rings that did not meet its specifications in certain T55 engines during scheduled maintenance that had now been "identified and isolated."
None of the O-rings "originated or were part of any Honeywell production or Honeywell-overhauled engines," it added.
Honeywell did not respond to questions about when the Chinook fleet would be back in the air.
Since it was first came into service in the early 19 60s, Boeing's CH-47 Chinook has remained the US Army's main soldier and supply transport aircraft.
Boeing declined to comment on the incident.
In late July the US Air Force temporarily grounded its fleet of about 300 Lockheed Martin F-35 fighter jets amid concerns that its ejector seats may be faulty.