Two police officers and a motorist have been injured in a collision during a police pursuit.
The police car, a Ford S-Max, was sounding its siren and flashing its blue lights when it collided with two cars in Danbury, Essex, this morning.
Officers had been following a green Fiat Stilo estate which was reported stolen from Suffolk when they collided with a blue VW Beetle and a blue Toyota Aygo on the A414, Maldon Road at 6.39am.
An Essex Police spokeswoman said the driver of the Aygo was taken by air ambulance to a London hospital. Both police officers were taken to Broomfield Hospital in Essex. It is not thought that any of their injuries are life threatening.
The spokeswoman said the Fiat Stilo stopped nearby and the two occupants ran off.
Two hours later, a 21-year-old was arrested in Danbury on suspicion of the theft of a motor vehicle and is being questioned by detectives.
Police later confirmed the driver of the Aygo, a 25-year-old woman from Maldon, Essex, suffered serious, "potentially life-changing" injuries.
An Essex Police spokesman said: "All the thoughts of every police officer concerned are with her and her family."
The driver of the VW Beetle was "badly shaken" but did not require hospital treatment.
Police said the crash is being investigated and officers have appealed for witnesses to come forward.
Chief Superintendent Tim Stokes said: "Only specially trained police officers are able to carry out pursuits of other vehicles.
"Any decision to authorise a pursuit must be a reasonable and proportionate response to the crime or other issue and proper procedures must be followed, including proper command and control."