Carlin driver Patrik Pasma had stopped on track due to a problem with his car and Monger was unsighted by another vehicle, careering into the back of the stricken machine at full speed.
On-ground medical teams and an air ambulance quickly arrived at the scene of the accident but the crash was so severe that they were unable to remove Monger safely from the car for some time.
Billy Monger crashed into Patrik Pasma at Donington Park
The 17-year-old racing driver was in the car for over an hour afterwards but according to ITV, he was conscious and has now been taken to hospital.
Pasma meanwhile was also hurt in the crash and will spend the night in hospital.
"Patrik Pasma was taken to the on-site medical centre for assessment," a Carlin statement said.
On-board footage of the crash shows Billy Monger's car hitting Patrik Pasma at high speed
"Patrik, who is fully conscious and able to communicate with team personnel, will now be transferred by ambulance to the Queen’s Medical Centre in Nottingham for further checks and observation overnight.
"Our thoughts remain with Billy Monger who was also involved in the incident."
Monger had picked up two podiums in his first four races of the F4 British Championship for JHR Developments.
But he was forced to retire from the second race of the day at Donington, which was won by Jamie Caroline.
"Monger has been carefully extracted from the car after suffering leg injuries, and has since been airlifted to the Queen’s Medical Centre in Nottingham for further examination," a BTCC statement said.
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