Emergency services are at the scene of an air accident involving an aircraft and a helicopter near Aylesbury.
,"A spokesperson for Thames Valley Police said officers were currently at the scene of an air accident near Waddesdon.
"The force is coordinating the response to the incident which was reported at 12.06pm today (17/11).
"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.
"In consequence of this incident it is expected that there will be some disruption to the road network around Waddesdon for the rest of the day," the spokesman said.
In a further update issued just before 4pm, the spokesman added: "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."
At 4pm, a spokesman for South Central Ambulance Service said: "We were called at 12.09pm to reports of a mid-air collision involving a helicopter and an aircraft at Upper Winchendon. We sent one air ambulance, two crews and one rapid response vehicle.
"There have been a number of casualties but we cannot say anything further at this stage."
The fire service sent a total of seven crews to the incident. Firefighters from Aylesbury and Haddenham are being supported by colleagues from Oxfordshire and Berkshire.
A spokesman for the Air Accidents Investigation Branch said: "The Air Accidents Investigation Branch is sending a team to investigate a mid-air collision involving an aircraft and a helicopter near Aylesbury."
The Press Association is reporting that both aircraft came from Wycombe Air Park, near High Wycombe.
Both aircraft involved in today's mid-air collision near Waddesdon are understood to have come from Wycombe Air Park, according to the Press Association.
It quotes a spokesman for the airstrip as saying: "Wycombe Air Park can confirm that at 12 o'clock local today we were informed of an incident north-west of Aylesbury involving two aircraft from Wycombe Air Park."
However, a spokesman refused to confirm the report when approached by The Bucks Herald and issued the following statement: "We were informed of an incident at 12.00 in the North West Aylesbury area involving two aircrafts.
"The emergency services are at the scene and the Air Accident Investigation Board have been informed and dispatched a field investigation team."
Wycombe Air Park's website describes says it is "more than just a place where aircraft land and take off, it's also a great place to relax with family and friends".
"We offer quality flight training for both pleasure and commercial goals. We look after more than 200 aircraft for club members and other airfield users including gliders, rotary wing aircraft and vintage aircraft such as Tiger Moths," the website says.
A spokesman for RAF Halton confirmed that none of its aircraft was involved.
Transport for Bucks said it was assessing the impact on local roads. In a tweet, TFB said: "A41 is NOT closed, #Aylesbury #Waddesdon. We are investigating any impact on local roads now, more info as we have it."
A spokesman for Bucks County Council said: "A Transport for Buckinghamshire technician drove through Waddesdon and around the area at 3pm this afternoon, following the reports of an air crash near the Manor grounds.
"There are no road closures and no traffic disruption, other than the usual Friday afternoon traffic. Emergency services remain on the scene, and our thoughts are with them and the affected families."
The national media has been reporting that the incident was either near or at Waddesdon Manor, but a spokesman confirmed that the accident was not on Waddesdon Manor land.
"This tragedy did not happen at the Manor nor have there been any casualties at Waddesdon Manor," the spokesman said.