Four lorries, a car and a van were involved in the crash
A Dutch lorry driver is being held on suspicion of dangerous driving after a pile-up on the M6 in Birmingham left another HGV driver critically ill.
The man, from Preston, Lancashire, and six others were hurt in the crash, which happened at 0540 GMT between Spaghetti Junction and Great Barr.
The motorway was shut for several hours but has since reopened.
Their HGVs collided on the northbound carriageway before one crossed over the central reservation and overturned.
It was then hit by several vehicles.
The motorway reopened northbound on Friday afternoon but remained shut between junctions 8 and 6 southbound until the early hours of Saturday.
The outside lane was expected to remain closed for longer because the central reservation needed to be repaired. Motorists were advised to avoid the area if possible.
The injured lorry driver, a man in his 40s, was airlifted to Selly Oak Hospital by police helicopter after suffering multiple injuries to his leg, hand and pelvis.
Five men and a woman suffered minor injuries and were taken to hospital for treatment.
The crash caused major congestion on the M6, M5 and M42 and the Highways Agency said long delays throughout Friday were likely.
Birmingham City Council said all major A roads near the crash scene had been congested.
Accident investigators and vehicle recovery teams were called to the scene of the crash, while 100m of all four lanes of the southbound carriageway were being resurfaced.
West Midlands Fire Service sent six crews to the scene and firefighters freed several people who were trapped in their vehicles.
It said the lorries were not carrying hazardous loads.
Six lanes of carriageway were closed