Four members of the United States Air Force have been confirmed dead after a refueling aircraft crashed in western Iraq during operations connected to tensions with Iran. The tragic incident happened on Thursday, raising concerns within the U.S. military.

According to United States Central Command, the KC-135 refueling aircraft went down at about 2 p.m. Eastern Time. Officials confirmed that four of the six crew members on board lost their lives in the crash.

Military authorities said the status of the remaining two crew members had not yet been fully confirmed, as search and rescue teams continue operations at the crash site. Another aircraft involved in the mission reportedly landed safely.

CENTCOM also stated that early investigations show the crash was not caused by hostile or friendly fire. The names of the deceased crew members are being withheld temporarily until their families are formally notified.