A US Navy helicopter carrying five service members crashed Thursday in the Gulf nation of Oman while conducting heavy lift operations.

The U.S. military did not give immediate details on the fate of the crew members, but an Omani air force official, speaking on condition of anonymity,  said that three of the crew has already been found and being treated in a hospital.

The MH-53E Sea Dragon, manufactured by United Technologies Corp’s Sikorsky Aircraft unit, crashed some 58 miles southwest of the capital Muscat. Lt. Greg Raelson, a spokesman for the Navy’s Bahrain-based 5th Fleet, said an investigation is already initiated.

According to a statement released, no hostile activity was suspected.

The downed aircraft, used for long-range mine sweeping, is assigned to Helicopter Mine Countermeasure Squadron 15, which is based in Norfolk, Va. However, no further details were available for report from the duty officer at the squadron base in Virginia.