There have been a number of casualties, following a mid-air collision involving a helicopter and an aircraft near Aylesbury in Buckinghamshire, according to South Central Ambulance Service.
At this stage, the service said that was all it could confirm.
Emergency services said they were called just after midday to the site after a collision in Upper Winchendon, near Aylesbury.
The Air Accidents Investigation Branch had said it was "sending a team to investigate a mid-air collision involving an aircraft and a helicopter near Aylesbury, Buckinghamshire".
Waddesdon Manor said on Twitter that the incident "did not happen at the manor, nor have there been any casualties at Waddesdon Manor", after initial reports said the collision had happened near the country house.
Both aircraft came from Wycombe Air Park, which is also known as Booker Airfield, near High Wycombe.
Thames Valley Police said there had been a number of road closures following the accident, which have now been lifted.
We're aware of a number of casualties following an incident this afternoon in Waddesdon, Aylesbury.— Thames Valley Police (@ThamesVP) November 17, 2017
There were a number of road closures following the incident, which have now been lifted.
We will provide further updates when available.
We can confirm that we are in attendance at the incident near Waddesdon.— TVAA (@TVAirAmb) November 17, 2017