A woman in her seventies is critically ill in hospital after a crash which killed three members of her family, including a baby girl.
A car and a lorry, travelling in opposite directions, collided on the B1404. A man aged 75, who had been driving the car, his 18-year-old female passenger and a one-year-old baby were all confirmed dead at the scene.
The only survivor from the car, a woman aged 74, was airlifted to James Cook Hospital in Middlesbrough with "life-threatening" injuries.
The crash happened at lunchtime on Wednesday on the road between Houghton-le-Spring and Seaham.
The impact was so hard the lorry careered through two hedges, before coming to rest 250m away on the fairway of Sharpley golf course. Its owner said the scene was horrifying to witness.
The lorry driver, a 42-year-old man from Hetton-le-Hole, was treated for whiplash. He was arrested on suspicion of causing death by dangerous driving.
Durham Police have not released the names of those who died, but confirmed they were all from the same family and were from the local area.