Several people fled a car after it crashed on the M25.
Police say officers were called at around 6pm yesterday (August 31) after a BMW hit a barrier near junction 17 for Maple Cross.
The collision caused significant damage but there was no sign of anyone from the BMW at the scene of the crash.
Hertfordshire Constabulary says one man was later found injured and was taken to hospital.
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A police helicopter was called in to search for three more males and circled the West Hyde area from around 6pm before leaving just after 6.15pm, flight tracking website Radar Box shows.
They were not found and enquiries are ongoing, police say.
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Radar Box also shows an Essex & Herts Air Ambulance landed off Chalfont Lane, West Hyde, at around 6pm, before taking off and heading back to its base in Essex at around 6.40pm.
Anyone who was driving in the area at the time and saw the collision or has dash cam footage is asked to contact Hertfordshire Constabulary, quoting ISR 641 of August 31.
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