The crash left a trail of cars and debris for 300m (984ft) along the motorway The M5 northbound carriageway remains closed after an eight vehicle pile-up which left a 21-year-old woman critically injured.
The woman was among seven people injured in the crash at Cullompton, near Exeter, between junctions 29 and 28 on Thursday.
Cars and debris were strewn along the carriageway for 300m (984ft).
Vehicles are being diverted at Exeter from the carriageway which is expected to re-open later.
A police and a military helicopter helped airlift injured passengers after the crash at about 2100 BST on Thursday.
A one-year-old girl was taken to hospital as a precaution.
Sgt Aaron Bevan of Devon and Cornwall Police said: “It was quite a major incident.
“At that time of night the M5 was very busy.”
He appealed for the driver of a blue articulated lorry which witnessed the crash but drove on to call the police because he could have “vital evidence”.
Firefighters using power-cutters and thermal imaging cameras released five people trapped in their vehicles.
Casualties were taken to Derriford Hospital in Plymouth where the critically injured woman is being treated, the Royal Devon and Exeter Hospital and Musgrove Park Hospital in Somerset.
A number of less seriously injured people are believed to have been treated at the scene.
This article is from the BBC News website. © British Broadcasting Corporation, The BBC is not responsible for the content of external internet sites.