Three people have died in a crash on the A1(M) which involved six vehicles, police said.
Two lorries and four cars were caught up in the crash at Bowburn, County Durham, at about 18:20 BST on Thursday.
Durham Police said three people from two of the cars died at the scene.
A man, 41, who was driving one of the lorries has been arrested on suspicion of causing death by dangerous driving, the force said.
A man who was driving a Toyota Hilux and a man and woman from a Vauxhall Crossland all died at the scene.
A police spokeswoman said formal identification was expected “to take some time” but families had been informed.
Several others were injured in the collision, with two people requiring hospital treatment, she said.
The spokeswoman said: “Due to the complexity of the scene, there is ongoing work to safely recover evidence and remove vehicles which will take some time.”
Det Supt Dave Ashton said it was a “harrowing incident” and has been “incredibly upsetting and distressing for those who witnessed the collision, and for the emergency responders, including police officers, firefighters and paramedics, who attended the scene”.
“Our thoughts are with the family and friends of those who have lost their loved ones,” Mr Ashton said.
Durham and Darlington Fire and Rescue Service said it had taken more than an hour to put out the lorry fire.
Seven crews, including a specialist unit from Tyne and Wear Fire and Rescue Service, were sent to the site, it said.
The Great North Air Ambulance was also deployed to transport casualties.