Four people have been killed after a helicopter crashed near Cley-next-the-Sea, north Norfolk on Tuesday.
The helicopter was an American HH-60G Pave Hawk based at RAF Lakenheath in Suffolk, a spokesman for the USAF confirmed. No British military involvement is believed to have been involved.
The incident occurred in north Norfolk
The 48th Air Wing of the US Air Force based at RAF Lakenheath tweeted: "We can confirm that one of our HH-60G Pave Hawk helicopters was involved in an incident during a training mission outside Cley-Next-The-Sea."
Pave Hawks are used for combat search and rescue, mainly to recover downed aircrew or other isolated personnel in theatres of war. The 48th Fighter Wing, also known as the Liberty Wing, is assigned to the United States Air Forces in Europe (USAFE).
In addition to HH-60G Pave Hawks, it is home to squadrons of F-15 Eagle tactical fighter planes and F-15E Strike Eagle dual-role fighters.
Local reports said that residents had heard F-15 planes flying over the scene of the crash. Helen Terry, 43, from Salthouse, near Cley, said: "We heard the helicopter fly over. We assumed it was just heading out to sea for training exercises. It's a daily occurrence and we're quite used to it.
An investigation has begun into the crash
"We live less than half a mile from where it's happened and we didn't hear any bang. The first we heard was when we saw emergency crews rushing to the area. It's something locals are used to and we've never had any safety concerns."
A resident who did not want to be named said: "We heard the helicopter fly over. There wasn't any bang but soon after we heard some jets fly over very low. It was obvious it was part of a search operation and it shook our house."
Earlier, Norfolk Police said: "We are currently dealing with a single helicopter crash in the Cley area, on the North Norfolk coast. There are believed to be four fatalities. Officers are on the scene, with a 400 metre area cordoned off."
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."
Police have said residents can stay in their homes but pedestrians and motorists are being diverted away as there is live ammunition on board, which could pose a threat to the public. A number of cordons are in place, closing nearby residential streets.
US troops onboard an Air Force HH-60 Pave Hawk helicopter
Around a dozen emergency vehicles from the fire brigade, coastguard and police are at the scene. Cley artist Rachel Lockwood, from the village's Pinkfoot Gallery, said: "We had never seen so many police cars and fire engines, so went to have a look.
"The beach road to Cley is sealed off. There are lots of fire engines near the Dun Cow pub at Salthouse. A helicopter is hovering over the marsh with a light beaming down."