An American military refueling plane involved in the operation against Iran crashed in Iraq on Thursday, U.S. Central Command said, with rescue efforts underway and the military still working to determine the situation’s impact. Central Command said two aircraft were involved—one landed safely while the other went down in western Iraq. Central Command also said it was not immediately clear whether there were casualties.

A U.S. official speaking to The Associated Press on condition of anonymity said the KC-135 aircraft that crashed had at least five crew members aboard. Another U.S. official, also speaking on condition of anonymity, said the other plane involved was also a KC-135 tanker. Central Command said “More information will be made available as the situation develops” and asked for “continued patience” to gather details and provide clarity to families of service members.

In a statement, Central Command said the crash was not due to hostile fire or friendly fire, and described the plane as “a loss.” The Associated Press reported that the tanker is the fourth publicly acknowledged aircraft to crash as part of the U.S. military’s operations against Iran.

The AP report also noted that last week three American fighter jets were mistakenly downed by friendly Kuwaiti fire. It said all six crew members safely ejected from the F-15E Strike Eagles and were in stable condition after being recovered, citing the U.S. account provided earlier.

The crash came amid a broader record of battlefield losses connected to the Iran war, the AP said. Seven American troops have been killed in combat during the war so far, while about 140 U.S. service members have been injured, including eight severely, according to the Pentagon. The report said six of the fallen service members were killed when an Iranian drone struck an operations center at a civilian port in Kuwait, and that they died one day after the U.S. and Israel launched their military campaign against Iran on Feb. 28.

The AP report said the Islamic Republic has retaliated with missiles and drones against Israel and several Gulf Arab states that host U.S. armed forces. It added that the seventh American service member died after being wounded during a March 1 attack on the Prince Sultan Air Base in Saudi Arabia. President Donald Trump and Defense Secretary Pete Hegseth have warned that the Iran war would likely claim more American lives before it ends.

Central Command’s account of the aircraft also placed the KC-135 in a long-running fleet. The AP reported that the tanker involved is based on the same design as the Boeing 707 airliner and entered military service more than 60 years ago, with upgrades over the years. It said KC-135 tankers typically have a crew of three, and that it was not immediately clear what role the extra crew members were serving aboard the flight.