A spokeswoman for the North Tees and Hartlepool NHS Trust said all nine walking wounded who had gone to the University Hospital of Hartlepool had been treated and discharged.

She said they had suffered minor cuts and other soft tissue injuries.

The spokeswoman said the University Hospital of North Tees treated 12 casualties - all children - who had slightly more serious injuries, but she said only two of these remained in hospital tonight.

Both are described as in a comfortable condition.

Shocked young eyewitnesses described how the minibus appeared to swerve to avoid a child that had run into the road.

The school minibus then ploughed into a fence and a tree where a crowd of passing youngsters were gathered.

Many of the injured are thought to have been from among the children on the street and not on the bus.

Details of exactly what happened are still sketchy but youngsters who witnessed the crash said pupils were running around covered in blood.

Peter Murphy, 14, a pupil at English Martyrs School, said: "There were a lot of groups of children going home from school when one boy ran out into the road in front of the bus.

"It swerved to try and avoid him and as a result it left the road and ploughed into the fence hitting some of the kids in the street.

"Other kids jumped out of the way and were running from the scene screaming.

"There was a lot of blood everywhere, it was horrible.

"After that I turned away because it was so unpleasant to look at."

Stacey Owens, 13, said: "There was people screaming and people were walking around the bus covered in blood.

"Children were just running away from the bus screaming and there was a number of children trapped under the bus."

The incident is now being investigated by Cleveland Police and the bus is still embedded in the fence outside English Martyrs School.

Sergeant Paul Dee, of Cleveland Police, said: "I am led to believe that the vast majority of the casualties were pedestrians."

The driver of the minibus has been spoken to and has given an account of what happened.

English Martyrs School headteacher Joe Hughes said everyone at the school had been left shocked by the crash. He said tonight: "Everyone is very concerned and very worried and our thoughts are with the students in hospital.

"We will be praying all through the night that the outcome is the best possible one."

English Martyrs School, a voluntary aided Catholic school, caters for 1,540 children between the ages of 11 and 18 and it is thought that the children on board the minibus were aged around 12 and 13.

Mr Hughes said that he understood there were about 26 children on board the bus and he understood also that it was fitted with seatbelts.

He added: "There are special plans in place for tomorrow to allow us to provide support to all of the students and staff in the school.

"The day will begin with a special staff meeting followed by a series of special assemblies for every year group in turn and counselling support will also be available in school for anyone who requires it."

Hartlepool Borough Council said it would be supporting the school through its childrens services departments.

John Collings, the assistant director of childrens services with the council, said tonight: "If we can support the school in any way we do have people working for the borough council who can offer that support and help."