It comes after major incidents were declared following "a number of casualties", emergency services said earlier.

Calday Grange all-boys grammar school and West Kirby all-girls grammar school confirmed one of its school buses was involved in the incident, which took place shortly after 8am on Friday.

A total of 54 people were on the bus - many were assessed at the scene on the M53 near Hooton.

A further two patients were taken to Alder Hey Children's Hospital with serious injuries, while a number of other patients were taken to surrounding hospitals for treatment of minor injuries, a spokesperson for North West Ambulance Service said.

A total of 50 children were transported to a casualty clearing centre at the emergency services training centre in Wallasey.

Of those, 39 have been discharged while the remainder have been taken to hospital for further treatment.

Chief Superintendent Graeme Robson of Merseyside Police said: "Family Liaison Officers are providing specialist support to both families and we are working with both schools and Wirral and Cheshire West Councils to ensure the necessary trauma support is in place for the children on the bus.

"We also know that other children from both schools were on buses travelling in convoy with the bus involved in the incident and they witnessed the incident. They too will be provided with specialist trauma support."

Firefighters helped passengers exit the schoolbus following the crash said Mark Thomas, area manager of Merseyside Fire and Rescue Service.

"Firefighters worked with emergency services colleagues at the scene to stabilise the vehicle. We ensured the scene was safe, and we assisted casualties exiting the bus," he added.

"Working jointly with our police and ambulance colleagues, shortly after we were able to assist the casualties onto a second coach to receive care away from the scene.

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"Our operations are currently scaling down, and currently we stay at the scene, in attendance, to preserve the scene with Merseyside Police whilst an investigation is conducted."

Joanne Clague, area director for North West Ambulance Service and Merseyside, said a major incident was declared "due to the potential number of casualties involved".

She said: "As a result, we sent a substantial number of ambulances, senior clinicians and our hazardous area response teams. A critical care doctor was also dispatched to the scene."

Simone White, director for children, families, and education at Wirral Council, said the council was "working closely" with the schools affected.

"On behalf of Wirral Council I offer my sincerest condolences to everyone affected by this tragic incident today," he said.

"We will continue to do whatever we can to help."

Children's hospital A&E 'extremely busy'

Alder Hey Children's Hospital declared a major incident but this has now been "de-escalated".

It said its accident and emergency department "remains extremely busy", adding: "Please only attend in cases of emergency."

Labour leader Sir Keir Starmer said: "My heart goes out to everyone affected by the tragic accident on the Wirral this morning. Unimaginably sad news."

Meanwhile, UNISON, said clinical supports workers in the Wirral involved in a local dispute over pay "immediately left the picket line" and members returned to be available on-call to help following the crash.

"Our thoughts are with everyone involved in the terrible school bus crash in the Wirral and all the emergency service workers responding to the incident," the union said in a statement.

Local Labour councillor, Sherin Akhtar, said the bus involved in the crash was a W3 service, which is shared between Calday Grange Grammar School and West Kirby Grammar School.

According to Calday Grange's website, the school bus route starts in the Chester suburb of Bache, making stops in Little Sutton, before joining the M53 on its route to West Kirby.

The M53 remains closed in both directions between junctions four and five.

It is expected to be closed for a number of hours while investigative work is carried out, according to police.

In separate statements on X, Calday Grange Grammar School and West Kirby Grammar School said: "We are aware of a situation involving one of our school buses on the motorway earlier today.

"We're actively gathering details and assisting affected students and their families."