The family of four U-S Air Force members who died in this helicopter crash have been notified.
Investigators are combing through the wreckage of the Pave Hawk aircraft, to understand why the military chopper went down in the marshland on England's east coast.
Bob Scully, Norfolk Police Chief Superintendent says, "there are a significant number of specialists from the royal air force, from the united states air force, all working together."
U-S officials say the helicopter was on a low-level training mission when it went down Tuesday night. The US air force works out of a nearby Royal Air Force base.
A second military helicopter flying in tandem at the time of the crash "set down" to try to help the crew.
Crash witness Michael Gilang says, "i was just out here and there were a couple of helicopter around. They were flying quite low. One sort of high-tailed that way, as if he were going land down on the beach. But clearly, he didn't."
Investigators say it could take several days to determine the cause of the crash and even longer to recover the chopper's ammunition.
The names of the dead American airmen are expected to be released within 24 hours.