A child has died and several others have been seriously injured when a school bus rolled west of Geelong.

At least 21 patients were taken to hospital after the crash on the Hamilton Hwy in Stonehaven about 8.20am on Wednesday.

It is believed the bus, carrying students from years 7 to 12, was turning left onto the highway from Friend in Hand Rd when it rolled, Victoria Police said.

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“There were 28 school students on board the bus at the time,” police said.

One female student suffered critical injuries and died at the scene.

Another student, a boy, was airlifted to hospital with serious but non-life-threatening injuries.

The bus driver and eight students sustained non-life-threatening injuries and were taken to hospital for treatment.

A further 11 students were taken to hospital for observation, police said.

The bus driver, a 76-year-old man from Hamlyn Heights, has since been released from hospital and is assisting police.

The exact circumstances surrounding the collision are yet to be established, and an investigation is ongoing.

Ambulance Victoria said two helicopter crews were sent in to help the injured children.Ambulance Victoria said two helicopter crews were sent in to help the injured children. Credit: 7NEWS

Ambulance Victoria said two helicopters, two mobile intensive care ambulances and four advanced life support paramedic road crews attended the scene.

The large number of patients were taken to either University Hospital in Geelong or Royal Children’s Hospital.

Detective Senior Sergeant Paul Lineham said the crash was “confronting” for first responders, and that the circumstances behind the crash are still unknown.

Lineham said the bus driver has passed preliminary blood and alcohol tests at the scene, but will be undertaking blood tests in hospital.

“Obviously there were some incredibly distressed parents at the scene,” he said.

“When it comes to children, as a parent myself, it really does hit home.

“My heart goes out to the parents when they first found out their children were involved, just their level of distress would have been incredible at the time.”

Lineham said police will investigate possible factors that could have led to the crash, including mechanical issues, speed and driver intoxication.

Victoria Ambulance area manager David Shearer said the children involved were likely to be affected for some time.

“It’s a really confronting day for those kids, and there are going to be many difficult days to come,” he said.

“A really tough day for everyone.”

Deputy Prime Minister and Geelong local Richard Marles earlier spoke of his sorrow over the tragic accident.

“My heart breaks hearing the devastating news of a school bus incident and death of a student in my hometown of Geelong,” Marles said.

“My first thoughts are with the family, friends and the school at this time and those who are injured.

“I am mindful the incident is still unfolding and further information is still coming to light, but I do know this will affect so many in Geelong as we are a tight-knit community.”

The highway has been closed in both directions between Inverleigh and Geelong.

Motorists have been advised to consider using the Geelong Ring Rd, Princes Hwy and Inverleigh-Winchelsea Rd, adding nearly 30km to the journey.

“The closure is under the control of Victoria Police, and the road will be reopened once investigations are complete and it is safe to do so,” Transport Victoria said.

Anyone who witnessed the incident or has CCTV or dashcam footage is urged to contact police.

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