A US helicopter crashed in Norfolk, England, killing all four crew members on board late Tuesday night.
The helicopter crashed while on a low-flying training exercise off the northern coast of Norfolk.
An investigation has been launched into the cause of the accident which authorities said killed all crew members, who are believed to be American.
No information on the identity of those killed will be released until next of kin have been informed.
Witnesses have reported hearing the helicopter "misfired" before it crashed. However, no official confirmation has been released.
Police say that because of the rough terrain in which the helicopter crash happened, and the live ammunition on board, the recovery of the aircraft will take a number of days.
With bullets scattered around the scene of the crash, which is the size of a football field, investigators have the tough task of securing the area.
Police also warn that debris could be washed into the ocean during high tide.
— BBC Breaking News (@BBCBreaking) January 8, 2014
MAP: Location of US helicopter crash site near Cley in Norfolk pic.twitter.com/gDmqfMl2qi
— BBC News Graphics (@BBCNewsGraphics) January 8, 2014
Chief Superintendent Bob Scully of Norfolk Police said it was too early to say what caused the helicopter crash, adding: "This is difficult terrain with marshland and tides coupled with wreckage containing munitions covering a large area."
"At the present time the coroner, who is responsible for the investigation into the deaths, is carrying out a daylight assessment of the situation and is then arranging for the deceased to be removed from the site," he said.
— Simon Fielding (@SimonFielding84) January 8, 2014
Speaking about the ammunition on board the helicopter, Scully says that, after the crash, ammunition was scattered around the area.
"That ammunition is not of any great significance. It is bullets, if you will, but those are scattered about that area that I just described to you, and so the site is hazardous to members of the public and those people that would normally visit this area for birdwatching and other nature-interest activities, so for the present time we will be assisting and working with the military to ensure public safety by restricting access to that area."
— John Stevens (@johnestevens) January 8, 2014
A second helicopter was flying in the area when the chopper went down and landed nearby to assist in recovery efforts.
The US Air Force says the investigation into the helicopter crash could take up to three months. However, they should be able to have an idea as to why it went down as soon as members of the other chopper can be debriefed.