A workhorse in Army aviation has been grounded after the service discovered a dangerous defect in the aircraft. The Army’s entire fleet of CH-47 Chinook helicopters has been grounded as of Tuesday, according to The Wall Street Journal. A series of engine fires in Chinooks has caused concern. The fires haven’t caused any deaths or injuries among U.S. service members. Defense officials familiar with the situation described the circumstances behind the grounding. The U.S. Army Materiel Command grounded the helicopters “out of an abundance of caution,” according to officials familiar with the action. Even though the flight restriction applies to every Chinook, officials are looking at over 70 aircraft containing a specific part that is thought to be connected to the issue. The Army has around 400 Chinooks in active service. These helicopters were manufactured with Boeing, with engines produced by the company Honeywell International Inc. Boeing declined to comment, according to The Journal. One Army spokeswoman pointed to fuel leaks as the cause of the engine fires. “The Army has identified the root cause of fuel leaks that caused a small number of engine fires among an isolated number of CH-47 helicopters and is implementing corrective measures to resolve this issue,” U.S Army spokeswoman Cynthia O. Smith said, according to Reuters. It’s not clear how long the grounding of Chinook helicopters will last. The move could prove detrimental to Army logistics, with the Chinook key to supplying Army units with necessary supplies. The Chinook helicopter entered service in 1962 and remains a mainstay cargo helicopter in the Army, according to Honeywell. Chinooks are also used for troop transport and have seen use in medical evacuation missions, as well as disaster relief efforts. The aircraft can lift a massive 48,000 pounds at 4,000 feet. The grounding comes as the Philippines considers a potential deal with the United States to acquire Chinook helicopters for military use, according to Defense News. The Philippines canceled an earlier deal with Russia to acquire Mi-17 utility helicopters before considering Chinooks as an alternative. Leaders of the Philippines feared that a financial transaction with the Russian government would leave the country vulnerable to western sanctions on Russia. This article appeared originally on The Western Journal.