WASHINGTON - An MH-53E Sea Dragon helicopter crashed near Oman on Thursday while conducting heavy lift support operations, and the fate of its five crew members remained unknown, the US Navy confirmed.

The helicopter, which was assigned to Helicopter Countermeasure Squadron-15, crashed 58 miles (about 92 kilometers) southwest of Muscat, Oman, the US Naval Forces Central Command said in a news release.

It said the crash was not caused by hostile activity, and the cause of the accident was under investigation.

The status of the five crew members was "still being determined," as another MH-53E helicopter assigned to the same squadron was on the scene to provide search and rescue assistance, the release added.