Seven officers have been taken to hospital following a collision involving five police vehicles and another car which was being pursued on Tyneside.
Northumbria Police said the crash happened on the northbound A1 near the Derwent Haugh Road junction, on the borders of Gateshead and Newcastle, at 2.27am on Wednesday.
The force said seven officers were taken to hospital with what it described as non-life threatening injuries.
Four have been discharged, two remain for observation and one is receiving treatment to a leg injury.
A spokesman said the two occupants of a BMW, which was being pursued at the time, were uninjured.
A man in his 20s has been arrested on suspicion of causing serious injury by dangerous driving, he said.
A woman, also in her 20s, has been arrested on suspicion of aiding and abetting dangerous driving.
Both remain in custody.
The collision happened on the A1 carriageway below the roundabout where gunman Raoul Moat shot Pc David Rathband, leaving him blind, in 2010.
The spokesman said officers attempted to stop a dark grey BMW M Sport in the Whickham area of Gateshead at about 2am due to concerns over the way it was being driven.
The car drove off and was later seen in the Swalwell area.
He said specialist officers from the roads policing unit got behind the car at 2.25am and a pursuit was authorised.
Superintendent Michelle Caisley said: “Firstly, we want to wish all the officers who have been involved in the collision a full recovery.
“We would also thank all those who attended the scene, including our colleagues from Tyne and Wear Fire and Rescue Service and the North East Ambulance Service.
“An investigation is under way to determine the full circumstances surrounding the incident and we ask anyone with information that may assist us to come forward.
“We would also ask people to avoid speculation both online and in the community which could impact the investigation.
“We recognise this incident has caused significant delays and thank motorists for their patience. The road closure has been necessary in order for our collision investigation team to conduct their inquiries.”
National Highways said the A1 will be closed between Swalwell in Gateshead and Denton in Newcastle in both directions into Wednesday afternoon.
A North East Ambulance Service spokesperson said: “We received a call at 2.29am on Wednesday April 9 to reports of a road traffic collision on the A1 northbound near Denton, Newcastle.
“We dispatched five ambulance crews, a specialist paramedic, a duty officer, two crews from our hazardous area response team and requested support from our colleagues at the Great North Air Ambulance Service who attended by road.
“Five patients were transported to hospital for further treatment.”
Images from the scene showed four marked police vehicles badly damaged, a car on its side, and debris scattered across the carriageway.
One of the police vehicles had its roof torn off.
Long after the crash, blue lights continued to flash on an unmarked police car which was crushed against the central reservation barrier.
A police detection dog was sent in to a dark coloured BMW which was wedged between the marked police cars.
The process of removing the damaged vehicles and lifting them on to low loaders was under way by lunchtime.
Northumbria Police have asked anyone with CCTV or dashcam footage of the incident to get in touch.
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