NEW: An investigation into the cause is expected to take several days, police say
Helicopter was on a low-level training mission when it went down
Pentagon has no word on status of those on board
Helicopter is described as a Pave Hawk, a modified version of a Black Hawk
Four U.S. Air Force personnel died after a military helicopter crashed Tuesday evening near Cley, on the North Sea coast of England, authorities said.
A news release from police in Norfolk said a U.S. Air Force Pave Hawk HH-60G helicopter from a British base in Lakenheath had crashed and the four people aboard were dead.
“I would like to pass on my condolences to the family, friends and colleagues of those US Air Force personnel who have sadly lost their lives in this tragic incident,” Sarah Hamlin with the Norfolk Constabulary said in a statement released Wednesday.
The Pentagon had no update on the official status of those on board. The Norfolk Constabulary said details on those killed would not be released until next of kin have been notified.
Police said a large area had been cordoned off as authorities responded and secured the site. An investigation into the cause of the crash is expected to take several days.
The RAF base said the crash occurred during an evening training mission while the helicopter was flying low.
Cley is 180 kilometers (about 110 miles) northeast of London.
According to the Air Force website, a Pave Hawk is a “highly modified” version of a Black Hawk helicopter that often carries a crew of two pilots, one flight engineer and one gunner.
CNN’s Barbara Starr contributed to this report.