Emergency services rushed to the scene close to the village of Waddesdon following reports of an incident shortly after midday.

The crash happened in Upper Winchendon, close to the grounds of Waddesdon Manor.

Analysts from the Air Accidents Investigation Branch, which investigates air accidents in the United Kingdom, confirmed the collision had involved a helicopter and a light aircraft and investigators have been dispatched to the scene.

Air crash investigators are only called to the scene of light aircraft incidents when fatalities have occurred.

Superintendent Rebecca Mears of Thames Valley said on Friday evening the aircraft were carrying two people each.

Where is Waddesdon Manor?

Police, the ambulance service and fire crews from Aylesbury, Haddenham, Oxfordshire and Berkshire attended the scene.

Earlier in the day, South Central Ambulance Service said the incident had caused "a number of casualties".

A spokeswoman 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 tweeted: "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."

Buckinghamshire Fire Brigade confirmed five fire engines are in attendance as well as two urban search and rescue vehicles. Thirty firefighters are also at the scene.

Both aircraft involved in the mid-air collision came from Wycombe Air Park, near High Wycombe, a spokesman confirmed.

A spokesman for the airstrip, near High Wycombe, said: "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."

The airstrip is located around 20 miles south of the crash site and offers flight training for rookie pilots.

The Civil Aviation Authority told Express.co.uk that one of the aircraft involved in the crash may have been from one of the flight training schools based at Wycombe Air Field.

A spokesperson said: "It appears one of the aircraft involved was a training flight."

They said Wycombe was one of the busiest airfields in England and saw a high volume of flight traffic.

Flight tracking records show a light aircraft took off from Wycombe Air Park today at 11.56am.

GPS records appear to have lost signal with the aircraft two minutes later over a village called Dinton - which is between the airfield and Waddesdon Manor.

Radar information shows the plane’s speed remained constant, but altitude rose slightly at the beginning of the flight, to 11.59. Then it dropped 1000ft in 45 seconds.

Records show the aircraft is a Cessna fixed-wing plane weighing 758kg, with the capacity for one pilot and one passenger.

The plane, built in 1982, was first registered to Wycombe Air Park in November 1986.

Latest records, from May, show it had spent 13,942 hours in the air.

Meanwhile, it appears that air traffic control services were reportedly closed for weeks due to staff shortages at Wycombe Air Park.

A Notice to Airmen (NOTAM) was issued warning pilots the Aerodrome control tower would be closed “due to staff shortage”.

However the notice added the air traffic zone surrounding Wycombe Air Park as well as gliding operation remained active.

A spokesperson for Wycombe Airpark said they were unable to comment when contacted by express.co.uk.

It is unclear how this may have affected the flight as more details emerge from the scene.

Aviation journalist David Learmount told the BBC that mid-air collisions are rare but can happen.

He said: ”It's actually a very busy area for light aircraft, with lots of small aerodromes where gliding takes place.

"However, the pilots who fly there should be well aware of this and be keeping a very close look out.

"They normally fly between 1,000 and 2,500ft (305-760m) so that they don't have to be under the strict control of air traffic control.

"Aviators have to keep their heads moving around all the time because an aircraft could appear suddenly out of nowhere."

A spokeswoman for Waddesdon Manor, a large estate near Aylesbury, said the crash had not happened on its grounds.

Waddesdon Manor is owned by the National Trust, and boasts 6,000 acres of farm and woodland.

Staff from the country estate helped direct emergency vehicles and a huge cordon has been put in place.

After news of the collision broke pilots in online forums were discussing whether so-called VMC conditions were in force.

VMC, or visual meteorological conditions, apply where conditions are deemed suitable for human piloting to take over from automatic instrumentation, so-called instrument meteorological conditions (IMC).

The boundary criteria between IMC and VMC are known as the VMC minima and are defined by visibility and cloud conditions.

However, it is believed weather conditions over Waddesdon were sunny and relatively cloud free at the time of the accident.

One pilot on a pilot’s online forum said: “It's always busy near WCO and I know I've been guilty in the past of paying too much attention to pointing passengers at the Rothschild palace and not enough to a sharp lookout.

“Hoping against the odds for a positive outcome.”

 Additional reporting by Jon Rogers, Rebecca Pinnington, Vincent Wood and Helen Barnett