A US Navy MH-53E Sea Dragon helicopter with five people on board has crashed off the coast of Norfolk, Virginia.
Four of those on board the helicopter have been rescued, according to officials.
US Coast Guard officials said they responded to a downed aircraft report at about 11:00.
In a bizarre coincidence, the incident came a day after another US military helicopter crashed in the county of Norfolk, England, killing four people.
The aircraft in Wednesday’s incident went down 18 nautical miles east of the Virginia coast. The cause of the crash is not yet known.
The US Navy MH-53E Sea Dragon helicopter had five people on board when crashed off the coast of Norfolk
Petty Officer David Weydert said that the missing fifth person was still being sought.
The Coast Guard cutter Shearwater and two MH-60S helicopters are taking part in the search.
The condition of the four rescued personnel has not been given.
The downed helicopter, assigned to Helicopter Mine Countermeasures Squadron 14 (HM-14), was on a routine training mission, the commander of Naval Air Force Atlantic said in a statement.
Norfolk is an important hub for the US military, and is home to Naval Station Norfolk, the largest naval complex in the world.
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A police helicopter crashed into a busy pub in Glasgow city centre killing at least eight people.
Three people inside the helicopter and five people inside The Clutha pub were killed after the Police Scotland aircraft came down at 22:30 on Friday.
Other 14 people are being treated for “very serious injuries” in hospitals across the city.
A major investigation is under way and the Air Accidents Investigations Branch will conduct an inquiry into the crash.
Dr. Jennifer Armstrong, medical director at NHS Greater Glasgow and Clyde, said that of the 32 people taken to local hospitals after the crash, 18 had now been treated and discharged.
She confirmed that 14 people were still being treated for serious injuries.
“The main injuries we have seen include chest injuries, head injuries, long-bone fractures and lacerations,” she said.
It is thought that about 120 people were in the pub at the time of the crash.
Many were rescued or escaped but others were trapped by a collapse on the left-hand side of the building.
Three people inside the helicopter and five people inside The Clutha pub were killed after the Police Scotland aircraft came down
The three occupants of the helicopter who died were two police officers and a civilian pilot.
A significant number of personnel from Police Scotland, The Scottish Fire and Rescue Service and Scottish Ambulance Service are still at the scene.
Police Scotland Chief Constable Sir Stephen House told a news conference on Saturday afternoon that they would remain there for some time.
Chief Constable House said the operation would go on “for many days yet”.
He paid tribute to the emergency service personnel who were working at the scene and the people of Glasgow who disregarded their own personal safety to help survivors in the aftermath of the crash.
Deputy First Minister Nicola Sturgeon told the same news conference that the increased death toll from the crash was “news that everybody today has been both dreading and expecting”.
Scotland’s First Minister Alex Salmond earlier described it as a “black day for Scotland.”
UK’s PM David Cameron paid tribute to the bravery of the “ordinary Glaswegians” who rushed to help.
Queen Elizabeth II has said her thoughts and prayers are with the victims of crash.
The Police Scotland helicopter which crashed was a twin-engine Eurocopter EC135 T2.
In a statement, Eurocopter said its experts were “on standby to support the investigation in every way possible”.
“An accident investigation team from Eurocopter is on its way to Scotland to assist the UK Air Accident Investigation Branch and the BFU (German AAIB) in its efforts to investigate the cause of the accident,” the statement said.
Helicopter operator Bond Air Services said it was working with the police and emergency services.
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