Road users are advised to find alternative routes as emergency services attend the scene.
Four people were killed on Friday after a mid-air collision between a light aircraft and a helicopter in southern England, police said.
Air crash investigators have been called to the collision site, in a dense woodland, alongside paramedics, firefighters and Thames Valley Police.
Both of the aircraft are understood to have come from Wycombe Air Park and collided near Waddesdon, in Buckinghamshire, shortly after midday.
Police chief Rebecca Mears said she could not yet give out the identities of the victims.
"Reports of an air accident near Waddesdon Manor".
Buckinghamshire Fire and Rescue Service said they now have seven vehicles responding to the incident, including fire engines as well as urban search and rescue vehicles.
The plane involved is a Cessna 152 with a capacity for one pilot and one passenger.
RAF Halton, which is around 10 miles away, said no military aircraft were involved.
"The force is coordinating the response to the incident which was reported at 12.06pm today".
A spokeswoman said: "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". While the South Central Ambulance Service has confirmed "a number of casualties" in the incident, no further details have been provided yet.
Emergency services rushed to the scene, with fire officers launching a drone over the fallen wreckage in a desperate search for survivors.
In May, a man was left fighting for his life after crashing a helicopter near Wycombe Air Park.
Has The Rebound Started In Foot Locker, Inc.?
Zacks Investment Research raised Foot Locker from a "sell" rating to a "hold" rating in a research note on Monday, October 23rd. The athletic footwear retailer reported $0.62 EPS for the quarter, missing the consensus estimate of $0.90 by ($0.28).
Gigi Hadid Drops Out of Victoria's Secret Fashion Show
AJ NumanKaty Perry has apparently been denied entry into China ahead of the Victoria's Secret Fashion Show in Shanghai on Monday. This isn't the only setback Victoria's Secret staff is facing while producing the 2017 show in Shanghai, according to reports.