(WASHINGTON) — Five American service members were killed in a crash on Friday night after their aircraft had a “mishap” during a training exercise and went into the eastern Mediterranean Sea, officials said Sunday.

U.S. European Command said in an initial statement on Saturday that the cause of the crash was under investigation but “there are no indications of hostile activity.”

The aircraft was conducting a “routine air refueling mission,” according to European Command’s latest statement. Further details were not provided.

The names of the dead have not yet been released, pending notification of relatives.

“Our thoughts and prayers are with the families of the fallen,” European Command officials said in the latest statement.

President Joe Biden publicly mourned the deaths, saying in a statement that military members “put their lives on the line for our country every day. They willingly take risks to keep the American people safe and secure. And their daily bravery and selflessness is an enduring testament to what is best in our nation.”

Acknowledging the crash occurred just before the Veterans Day memorial weekend, Biden said, “We once more affirm the sacred obligation we bear to those who volunteer to serve our nation as well as their families, caregivers, and survivors.”

“Jill and I are praying for the families and friends who have lost a precious loved one—a piece of their soul. Our entire nation shares their grief,” the president said.

ABC News’ Fritz Farrow contributed to this report.

This is a developing story. Please check back for updates.

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