An investigation started on Wednesday into the cause of a US military helicopter crash on the east coast of Britain, in which all four crew members were killed, dpa reported.
The US Air Force HH-60G Pave Hawk crashed late on Tuesday near Salthouse in the county of Norfolk as it was performing a "low-level training mission", according to a statement from RAF Lakenheath, a USAF-operated base in nearby Suffolk.
US military officials were coordinating their efforts with local police and the British Ministry of Defence, the statement said.
The investigation is being hampered by the geography of the area and the munitions from the crashed helicopter among the debris, said chief superintendent Bob Scully of Norfolk police force.
"We have currently cordoned off about 400 square metres of the marshland area," he said. "The crash site itself I would describe as an area of debris on difficult terrain on the marsh that's about the size of a football pitch."
"It's not on the beach, although there are some bits of debris which are vulnerable to high tide," he added.