Live bullets are strewn across the scene of the helicopter crash at Cley as police and military experts probe the cause of the accident, which killed four USAF personnel.
Members of the public are being urged to stay away from the site on the marshes off Cley and Salthouse for safety reasons, and to allow the investigation to proceed unhindered.
The crash scene is the size of a football pitch, and police and military staff are at the scene - alongside a second helicopter, which was taking part in a military exercise when the other helicopter crashed.
A strict cordon remains in place around the Norfolk Wildlife Trust nature reserve, and those involved in the investigation include Ministry of Defence, Air Accident Investigation Branch, US Air Force and HM Coroner.
Two helicopters were involved in the training activity last night and following the crash the second aircraft landed nearby to assist.
Speaking from the scene, Chief Supt Bob Scully said: 'The crash site is about the size of a football pitch, with difficult terrain which makes this a challenging and lengthy process.
'This is mainly on marshland although some debris which was close to the beach has been moved as it would be vulnerable to high tide.
'Further close examinations of the scene will take place this morning and the bodies of the deceased will be removed once this has taken place.
'The helicopter was carrying ammunition this was in the form of bullets which are scattered across the site, which is why the restrictions are necessary.
'We would like to thank the local community for their patience and understanding at such a challenging time and our thoughts remain with those affected by this tragic incident.'
Specialist military personnel will attend to assess the environmental impact while the A149 remains closed through Cley. Access to Beach Road and East Bank is also restricted and there is no coastline access to the crash site.
The crashed aircraft is a USAF Pave Hawk HH60 helicopter from RAF Lakenheath, which came down at the north end of East Bank at around 7pm.
Names of the airmen killed in the crash will be released 24 hours after next-of-kin notifications.
The aircraft, assigned to the 48th Fighter Wing, was performing a low-level training mission along the coast when the crash occurred.
A second helicopter from RAF Lakenheath was also in the area at the time of the crash and set down on the marshes to try to assist, this was within the cordon and so this aircraft remains at the scene while inquiries are ongoing.
A five-mile radius exclusion zone for any aircraft in the north Norfolk area has been put in place.
Due to the geography and the munitions from the crashed helicopter, inquiries into the cause of the collision, the recovery of the wreckage and second aircraft and an environmental assessment are expected to take a number of days to complete.
• Local reaction to helicopter crash• Video footage of helicopter believed to be involved in crash• Norfolk Wildlife Trust staff helped emergency services at scene of crash• About the Pave Hawk helicopter• The marsh area where the helicopter went down
Last night people in the area spoke of their shock at the tragedy and told of hearing a 'heavy and very unusual' sound overhead as the helicopter plummeted into marshland.
Peter and Sue Mcknespiey, who run Cookies Crabshop in Salthouse, heard what sounded like a helicopter and then jets flying overhead before becoming aware of fire engines, police and emergency services outside.
She said: 'It just seemed an unusual thing. It didn't seem normal because it was so low and they don't fly low anymore.'
North Norfolk MP Norman Lamb said the crash was 'utterly tragic', adding: 'My heart goes out to the families of the crew, and it is all the more difficult because I suspect the families are from a long way away and the news is just filtering through.
'It is highly traumatic too for the local communities but it was quite close to the villages and could have been even more horrific if it came down on buildings.'
Norfolk Fire and Rescue Service said six fire crews were in attendance until around 11.30pm.
A spokesman for the Royal National Lifeboat Institution said: 'We were asked for three lifeboats to respond to reports that an aircraft had possibly ditched in the sea.
'Lifeboats Wells, Sheringham and Cromer were launched at the request of the coastguard but were stood down when it was confirmed that the aircraft had come down over land.'
Did you witness anything? Contact the newsdesk on 01603 772443 or email newsdesk@archant.co.uk
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