A U.S. Air Force Pave Hawk helicopter crashed in the coastal marshes of eastern England during a training mission on Tuesday night, killing all four crew members aboard, officials said.

The helicopter crashed at about 6 p.m. local time near Salthouse on the Norfolk coast, a statement from the U.S. Air Force said. The aircraft was based at the nearby Royal Air Force station in Lakenheath, Suffolk County, which hosts USAF units and personnel.

The helicopter, assigned to the 48th Fighter Wing, was flying low at the time of the crash, the statement added.

In Washington, a U.S. defense official said the accident killed the four U.S. Air Force crew members aboard. The official spoke on condition of anonymity because he was not authorized to discuss the crash publicly.

Emergency workers from the fire brigade, coast guard and police were at the scene.

Police in Norfolk County said they believe there is ammunition onboard the helicopter, and the scene was cordoned off so that experts could ensure the area was safe.

Officials said family members would be notified before information on the victims was released.

Pave Hawks — a modified version of the better-known Black Hawks — are often used for combat search and rescue missions, mainly to recover downed air crew members or other personnel during war and other hostile situations.

They typically practice flying low and fast, often at altitudes of hundreds, rather than thousands, of feet.

Pave Hawks have been deployed in numerous overseas missions, including to Japan in the wake of the tsunami in 2011 and to support operations in Afghanistan, Iraq and Libya.