A Bradford bus driver and a passenger were seriously injured when the vehicle veered off the road and crashed into a garage.
Around 30 passengers on the bus were injured and taken to hospital.
The First bus service had been travelling from Bradford to Huddersfield when the incident happened.
A spokesman for First Bus said: "We can confirm the driver of the bus has been seriously injured in the accident. He is from the Bradford area."
Emergency services were called to the A641 Bradford Road in Huddersfield after the crash at 10am yesterday.
Passengers had to be cut out of the bus from windows as fire crews attempted to reach them with ladders. A West Yorkshire Police spokesman said: "Two people were seriously injured when the bus veered off the road.
"The full details of what occurred prior to the collision are not yet known."
The vehicle was believed to have left the road and hit a lamppost and a wall before crashing into a garage, demolishing it.
Five ambulances were sent to the crash scene and paramedics treated passengers at the roadside before they were taken to the Huddersfield Royal Infirmary. Most were suffering from whiplash and cuts and bruises. Debris from the accident was strewn across the road, which was closed to traffic and pedestrians.
Diversions were put in place causing delays to motorists.
The crash is being investigated by the Collision Investigation Unit of the West Yorkshire Police.
The spokesman for First said the firm would be conducting its own investigation.
Anyone who saw the accident should call Huddersfield police on (01484) 436845.
e-mail: jennifer.sugden@bradford.newsquest.co.uk
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