CANBERRA, Australia (AP) — A truck driver was charged Wednesday after seven children were hospitalized with serious injuries when he rear-ended a school bus on the outskirts of Melbourne in southeastern Australia, officials said.

The dump truck the 52-year-old man was driving hit the back of a school bus carrying 45 students and caused it to overturn Tuesday afternoon at an intersection in Eynesbury, a semi-rural community west of Melbourne, police said. Head injuries, arm amputations and suspected spinal injuries were reported by a hospital official.

The truck driver, whose name has not been made public, was charged with four counts of dangerous driving causing serious injury, a police statement said.

He will appear via a video link in the Melbourne Magistrates Court later Wednesday, police said.

Police Superintendent Michael Cruse said more charges were likely.

“Speed will be considered as well as part of the investigation,” Cruse told reporters.

Cruse paid tribute to passersby and the injured bus driver who helped children from the bus.

“It’s a really confronting scene. Some of the injuries are really very traumatic and that would be a difficult scene for a passerby to come across, and then to have acted the way they did is really admirable,” Cruse said.

Exford Primary School Principal Lisa Campo drove the short distance from the children’s campus to the crash site and was among those who rendered help.

“I didn’t know what I was going to see. I honestly thought I’d be just be there comforting some distressed kids who had been in been a minor collision,” Campo told reporters. “I didn’t ever expect to see that and hope I never see that again.”

A total of 21 children where initially taken by ambulance from the scene for medical care and seven of them remained hospitalized Wednesday.

One of the children was in intensive care, Royal Children’s Hospital Melbourne CEO Bernadette McDonald said, noting the children range in age from 5 to 11 years old.

“The children have suffered multiple and traumatic injuries including partial and complete amputations of arms, multiple crushing injuries, severe lacerations of the head and body, head injuries, glass shard injuries and three patients are … being monitored carefully in terms of spinal injuries,” McDonald told reporters.

She also said the hospital was assisting some extremely traumatized families, adding, “We’re working extremely hard to provide that trauma support and care that they will need, not just now but in the coming weeks and months as well.”

McDonald said one child lost an entire arm but she did not elaborate on how many of the injured had partial amputations.

About six children were temporarily trapped in the wrecked bus, the Country Fire Authority said. Emergency crews entered the bus through a skylight in its roof, and the smashed-out windshield was used as the main emergency exit.

Paramedics assessed dazed victims who didn’t appear to need hospitalization in the grass surrounding the crash site. The bus driver was taken to a hospital with minor injuries but was not admitted. The truck driver was not injured.

At the time of the crash, the children were returning to school after competing in an athletics event.