A total of 24 people, most of them international students, have been taken to hospital after their bus ran off a road in Gidgegannup, 40 kilometres north-east of Perth.

The incident occurred just before 8:00pm (AWST) last night on Toodyay Road, near the intersection of The Springs Road, close to the town's centre.

The school bus rolled into a ditch and some of the students were trapped inside.

Firefighters returning from another job stumbled on the crash scene and they used jaws of life to free those trapped in the wreckage.

Paramedics used 11 ambulances to ferry the students and three adults, including the driver, to three separate hospitals.

Eight were taken to Princess Margaret Hospital, another five passengers to Royal Perth, and eight to Swan Districts for treatment.

Some students were trapped when the mini-bus went off the road into the ditch. ( ABC News )

Some have broken bones and medical staff say although they have been traumatised, their injuries are not life-threatening.

The students, believed to be aged 14 to 16, are from Indonesia and Malaysia, and were on their way to Lake Leschenaultia - another 10 kilometres down the road.

A bus was sent to bring the remaining people back to Perth.

The accident is being investigated by officers from the Major Crash unit.

The incident is just eight kilometres from where Morangup mother Jess Seager and her sons Jayden, aged six, and three-year-old Cody, were killed on the same road when their car collided with a truck in July last year.

Community meetings followed their deaths, with residents warning authorities about the dangers of that stretch of road.