A 38-year-old woman is in hospital with serious injuries, that are believed to be life-threatening, following a collision on the M66 yesterday afternoon.
Three children were also taken to hospital with serious injuries.
A 22-year-old man was arrested at the scene on suspicion of causing serious injury by dangerous driving.
He remains in custody for questioning.
Emergency services were called to the scene on the southbound carriageway between junctions 3 & 4 at around 3 pm.
Police are now appealing for witnesses and information.
Sergeant Matt Waggett from GMP Serious Collision Investigation Unit said: “I would like to thank the members of the public who selflessly helped at the scene and called 999, as well as those who assisted when police and emergency services arrived on scene.
“I urge anyone who may have witnessed this incident to please come forward and share any footage, dashcam or mobile footage, with police.
"No matter how small you think it is, it could prove vital to our investigation."
Information can be shared by calling GMP's Serious Collision Investigation Unit on 0161 856 4741 quoting incident 2254 of 13/05/2023.
A report can also be made via GMP's website: www.gmp.police.uk
Alternatively, call the independent charity Crimestoppers anonymously on 0800 555 111.