Eight people were killed when the minibus they were travelling in crashed with two lorries on a motorway.
Four other passengers – including one child – were taken to hospital after the collision on the southbound carriageway of the M1 near Newport Pagnell, between junctions 15 and 14.
The drivers of the two lorries were arrested in connection with the incident in Buckinghamshire.
A 31-year-old man from Worcestershire has been arrested on suspicion of one count of causing death by dangerous driving and one count of driving a motor vehicle when alcohol level above limit.
A 53-year-old from Stoke-on-Trent is also in custody, on suspicion of one count of causing death by dangerous driving.
It is thought the minibus had travelled from the Nottingham area, Thames Valley Police said.
The vehicles involved in the crash were travelling in the same direction
Emergency services were called shortly before 3.15am on Saturday and the road was closed until the early afternoon to allow recovery work to take place.
Chief Inspector Henry Parsons from the joint operations unit for roads policing, said: “Our thoughts are very much with the families of those involved in this morning’s collision and we are currently working to locate and inform their next of kin.”
He asked for any witnesses, or anyone with information, to call the 24-hour Thames Valley Police enquiry centre on 101, quoting URN 214 of August 26.
Pictures of the vehicles appear to show a FedEx lorry with its cab crushed and the cab of a lorry with AML Logistics printed on the trailer twisted around to the side. Another image shows what appears to be the crumpled wreckage of the minibus on the back of a flatbed truck. Broken glass and debris from the collision is scattered across the tarmac.