Eight people are dead and four others have been taken to hospital after a crash on the M1, Thames Valley Police has said.
The crash, involving two lorries and a minibus, happened near the town of Newport Pagnell, in Buckinghamshire, at about 3.15am.
All eight victims were travelling in the minibus, as were the four injured passengers of whom one was a child, police said.
Images posted online suggested the crash took place near an exit ramp, and showed the wrecked minibus had been flattened in the collision.
Both lorry drivers have been arrested on suspicion of causing death by dangerous driving, and are in custody, police said. One, a 31-year-old from Worcestershire, is also suspected of driving while over the alcohol limit.
One of the lorries belonged to the mail courier company FedEx.
In a statement to The Independent, FedEx said: "We are aware of the tragic accident that occurred last night on the M1 motorway, junction 14 in the UK with a FedEx truck involved.
"Our deepest thoughts and concerns are with all of those involved.
"Safety is of the utmost importance to FedEx, and we are cooperating fully with authorities but have no further information at this time."
Thames Valley Police said all three vehicles were travelling in the same direction, and that the minibus was believed to have come from the Nottingham area.
The motorway has re-opened southbound between Northampton and Milton Keynes.
Chief Inspector Henry Parsons, of the Joint Operations Unit for Roads Policing, said: "I would appeal to anyone who witnessed the collision and has not yet spoken to officers to please contact us.
"Anyone who has any information which could assist the investigation should call the 24-hour Thames Valley Police enquiry centre on 101, quoting URN 203 of 26/8."
