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The lorry driver was en route from Manchester to Devon when his Volvo vehicle struck the single-decker bus near to junction three of the M5 at Halesowen.
The driver, whose family had travelled from the south-west to be with him in hospital, has yet to be named by police.
The Central Motorway Police Group was alerted to the crash at 6.24am on Saturday and emergency crews treated more than 20 bus passengers, who were being driven from Birmingham to the Evesham area of Worcestershire.
A 35-year-old man from the Smethwick area who had been travelling on the bus was confirmed dead at the scene and another passenger remains in a critical condition.
The southbound M5 was closed for around eight hours and a detailed investigation into the cause of the collision is under way.
Inspector John Thompson, from the Central Motorway Police Group, said: ``This tragic incident has now claimed its second life.
``Our thoughts remain with the friends and family of those who have died during this difficult time.''
West Midlands Police said specialist family liaison officers had been appointed and are supporting both families.
A dedicated hotline for concerned relatives which opened in the immediate aftermath of the incident has now closed, but police have revealed that embassy officials called the service offering support to any foreign nationals involved in the crash.
The bus, which was not fitted with seat-belts, was reported to have broken down in the nearside lane of the M5 before it was struck by the heavy goods vehicle.
Witnesses and a survivor of the crash said the accident happened after the coach came to a halt close to a footbridge in Bartley Green, Birmingham.
The driver's side of the lorry's cab was left embedded in the rear nearside of the coach following the collision, which also left debris strewn across the approach to the footbridge.
Signs warning road users of fog in the area had been active since 4.46am, but police declined to speculate whether low visibility was a contributory factor in the collision.
Martin Stott, of the Highways Agency, told a press conference that signs warning of an incident and urging drivers to slow down were put in place after an initial call from a member of the public saying the coach had broken down.
Fog warnings were already in place, Mr Stott said, adding: ''We'd set information across the network on our display signs to say that there was fog and to slow down.''