Five U.S. service members were killed Friday evening after their aircraft suffered a mishap and crashed into the eastern Mediterranean Sea, the Pentagon revealed Sunday.

The mishap took place “during a routine air refueling mission as part of military training,” and all onboard the aircraft were killed, U.S. European Command (EUCOM) said in a brief statement.

An earlier release from EUCOM stressed that the aircraft crash “was purely related to training and there are no indications of hostile activity.”

The command gave no further details on the type of aircraft involved in the crash, the military service it belonged to, or the exact location or timing of the accident.

Nearby U.S. military aircraft and ships began search-and-rescue efforts immediately, and the incident is under investigation.

“Out of respect for the affected families, and in accordance with Department of Defense policy, the identities of the crewmembers are being withheld until 24 hours after next of kin notifications have been completed,” according to the statement.

“Our thoughts and prayers are with the families of the fallen,” it added.

The Pentagon has moved additional U.S. forces to the Middle East following the Oct. 7 attack by Hamas militants on Israel. The U.S. military deployed the USS Gerald R. Ford strike group to the eastern Mediterranean and the USS Dwight D. Eisenhower strike group to the Persian Gulf.