Four people have died in a mid-air collision between a light aircraft and a helicopter near Aylesbury, Buckinghamshire, police have confirmed.
The crash happened in dense woodland near the historic Waddesdon Manor. Staff there directed emergency services to the scene.
Two people were aboard each aircraft, Thames Valley Police Superintendent Rebecca Mears said at a press conference on Friday evening.
She added it was “too early to tell” what caused the crash.
Aerial footage showed the wreckage but police cordoned off the area, restricting access.
Police said their examination of the site would resume at first light on Saturday and they expect to be there until at least Monday.
The plane was a Cessna 152, a light two-seater aircraft. Police gave no details of those who died, saying they were still notifying their next of kin.
South Central Ambulance Service said: “We received the call at 12.09pm for a mid-air collision involving a helicopter and an aircraft in Upper Winchendon, near Aylesbury.
“We sent a number of resources to the scene, including a Thames Valley air ambulance, two ambulance crews, two ambulance officers and a rapid response vehicle.
“There have been a number of casualties at the scene, but at this stage this is all we are able to confirm.”
Thames Valley Police said in a statement the crash was reported at 12.06pm on Friday.
Both aircraft involved in the mid-air collision near Waddesdon, Buckinghamshire, came from Wycombe Air Park, near High Wycombe, a spokesman said.
In a statement the airfield said: “Wycombe Air Park can confirm that at 12.00pm we were informed of an incident north west of Aylesbury involving two aircraft from Wycombe Air Park.
“Emergency services are at the scene and the Air Accident Investigation Branch have been informed and have dispatched a field investigation team.”
Police added: “Officers are currently at the scene of an air accident near the village of Waddesdon near Aylesbury.
“The Air Accidents Investigation Branch has been informed and staff are en-route to the scene. Fire and ambulance services are also in attendance and preservation of life is first priority.”
The Air Accidents Investigation Branch said it had sent of a team of investigators.
According to the Press Association, the Cessna had flown almost 14,000 hours as of May and had previously suffered substantial damage to its landing gear, propeller and engine following a crash at a Cornish airfield in 1993.
An archived report by the Air Accidents Investigation Branch (AAIB) shows the pilot admitted that accident was caused by his “misjudgment and lack of experience”.
A member of the Rothschild family has told of her shock after a mid-air collision between a helicopter and an aircraft missed her by five minutes.
The woman, who did not want her full name published, told the Press Association she heard a loud bang while she was driving her car to a dog grooming event, near Waddesdon, in Buckinghamshire.
Just five minutes earlier she had been picking a plant in the Wilderness Woods, the scene of the crash site, on the Waddesdon Estate.
“I’m totally shocked,” she said. “I heard a loud bang, which I thought was a car crash.”
Waddesdon Estate gardener Len Bellis described how he found the “burning wreckage” minutes later.
He had been working nearby when he heard a “horrendous noise”.
Mr Bellis said two men came running towards him from the woods shouting, “did you see it, did you see it?”
He said one of them told him he heard a plane “stuttering” just before the crash.
“I just came across the wreckage,” said Mr Bellis, who described the light aircraft as a “wreck” and “non-existent”, apart from the 5ft burning fuselage.
He said he later found out he was just 10 yards from a body in the undergrowth.