WASHINGTON, July 19 (Reuters) - A U.S. Navy helicopter crashed in Oman on Thursday and the fate of its five crew members was unknown, the U.S. military said, even as it ruled out hostile activity.

The helicopter, a MH-53E Sea Dragon, manufactured by United Technologies Corp's Sikorsky Aircraft unit, crashed 58 miles southwest of Muscat while flying a heavy load in support of the Omani government.

"The crash was not due to any sort of hostile activity and the status of the five crew members is still being determined," said the statement from U.S. Naval Forces Central Command, adding the crash was under investigation.