Emergency services have said "preservation of life is first priority"
British police have confirmed that four people have died following a mid-air collision involving an aircraft and a helicopter in England.
The crash is understood to have happened close to Waddesdon Manor, though a spokeswoman for the estate said it had not happened "on its grounds".
Both aircraft came from Wycombe Air Park, also known as Booker Airfield, which offers flight training.
The plane that crashed is thought to be a Cessna 152, which has capacity for one pilot and one passenger.
A spokesman for the airstrip, near High Wycombe, said: "Wycombe Air Park can confirm that at 12pm local today we were informed of an incident north-west of Aylesbury involving two aircraft from Wycombe Air Park."
A police statement said: "Thames Valley Police is currently at the scene of an air accident near the village of Waddesdon near Aylesbury.
"The force is coordinating the response to the incident which was reported at 12.06pm today (17 November).
"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."
At around 4pm on Friday, they issued an update, and said: "We're aware of a number of casualties following an incident this afternoon in Waddesdon, Aylesbury.
"There were a number of road closures following the incident, which have now been lifted. We will provide further updates when available."
RAF Halton, 10 miles away, said no military aircraft had been involved.
Bucks Fire and Rescue is also in attendance, having sent seven vehicles including urban search and rescue.
A statement on Twitter read:
Firefighters currently assisting other emergency services at scene of air accident near Waddesdon. Air Accidents Investigation Branch informed. Disruption to road network around Waddesdon likely for the rest of the day— Bucks and MK Fire (@Bucksfire) November 17, 2017
Air accident investigators have also been sent to the scene.