Police are investigating whether a lorry was involved in a school bus crash which left more than 20 people, mainly schoolchildren, injured.

Up to 53 children of around 14 years of age were travelling in the bus when it overturned down an embankment on Holme Lacy Road in Hereford shortly after 8.20am.

Witnesses reported that a lorry was involved in the accident but did not stop.

A spokeswoman for West Mercia Police said: "The police investigation into the circumstances of the motoring collision continues and the involvement of another vehicle is currently being investigated."

The force said that 21 children were taken to hospital from the scene and a further five attended later to receive treatment for cuts and bruises.

The female driver is thought to be receiving treatment in intensive care for chest and abdominal injuries.

Most of the children are pupils at St Mary's Roman Catholic High School, with an additional four studying at nearby Bishop of Hereford's Bluecoat School.

A spokeswoman for PW Jones Coaches, which operates the bus, said : "A coach that was carrying schoolchildren went off the road and the children are saying that a lorry was involved and didn't stop.

"The coach had pulled over to stop on a grass verge and it gave way."

Seven ambulances, a paramedic area support officer, two senior paramedic officers and the Midlands Air Ambulance from Strensham were sent to the scene.

A doctor for the Mercia Accident Rescue Service was also sent but diverted to the hospital to assist with triage of casualties as they arrived at A&E.

A West Midlands Ambulance Service spokeswoman said: "Crews arrived to find a bus at the bottom of an embankment lying on its left-hand side.

"All of the passengers on board had managed to get out of the bus before the crew's arrival.

"However, the woman driving was trapped for a period of time.

"With the assistance of the fire service, the woman was extricated and treated for chest and abdominal injuries.

"She was immobilised using a neck collar and spinal board before being conveyed to Hereford County Hospital."

A second bus was taken to the scene to help transport around 20 uninjured pupils back to their school with a senior paramedic officer.

Sara Catlow-Hawkins, headteacher at Bluecoat School, said that both schools involved had dispatched staff to the scene to help their pupils.

"All of them were shaken and some had suffered cuts and bruises," she said.

"The students behaved and worked with each other in a tremendously supportive way, the two schools worked well together and the emergency services were superb.

"Both schools would like to say that our prayers go out to the driver and her family."