(NEW YORK) — Six Americans were among the eight international peacekeepers killed when their helicopter crashed in Egypt’s Sinai Peninsula.

The international observer mission in the Sinai Peninsula said all indications are that the crash, which also left one American peacekeeper injured, was the result of an accident.

The peacekeepers are part of the international mission that oversees the enforcement of the 1978 Camp David Peace Accords between Egypt and Israel.

“During a routine mission in the vicinity of Sharm el-Sheikh, Egypt, nine members of the Multinational Force and Observers (MFO) were involved in a helicopter crash,” the MFO said in a statement issued on its website.

“One U.S. MFO Member survived and was medically evacuated,” the statement added. “Names are being withheld pending notification of next of kin.”

The Israeli Defense Forces later confirmed that the injured American had been flown by a search-and-rescue team to an Israeli hospital for medical treatment.

“The Defense Department is deeply saddened by the loss of six U.S. and two partner nation service members in a helicopter crash in the Sinai Peninsula operating with the United Nations Multinational Force and Observers (MFO)” said Acting Defense Secretary Christopher Miller in a statement.

“Yesterday we recognized the sacrifice of millions of American veterans who have defended our nation for generations, and today we are tragically reminded of the last full measure our uniformed warriors may pay for their service,” said Miller. “I extend the Department’s condolences to the families, friends and teammates of these service members.”

There are 452 U.S. military personnel among the force of 1,154 international peacekeepers that is part of the legacy mission in the Sinai Peninsula to enforce the 1978 peace treaty between Egypt and Israel. The treaty called for an enduring observer mission to ensure Israel’s return of the peninsula to Egypt.

The Pentagon recently assessed whether to keep participating in the mission, but ultimately decided it was required under the treaty.

Active duty military personnel were assigned to the mission for decades, but in recent years it has been carried out by National Guardsmen.

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