A U.S. military helicopter crashed on the eastern English coast, killing the four people aboard, officials said Wednesday.

The crash occurred Tuesday and British authorities launched an investigation to determine the cause of the accident.

Once the local police have concluded their initial examination, the investigation will pass to British and U.S. aviation authorities, Norfolk police superintendant Bob Scully said.

A police cordon some 400 square meters (about 4,300 square feet) in size was established in the marshy area where the Pave Hawk went down, Scully said.

The crash happened in an area considered to be a nature reserve and ammunition was found scattered at the site, the superintendent said.

The U.S. Air Force chopper crashed near the town of Cley-next-the-Sea, on the eastern coast of Norfolk, while on low-altitude training maneuvers.

The identity of the victims will not be revealed until their next-of-kin have been notified, although on Tuesday it was announced that no British military personnel were involved, Scully said. EFE