A school bus has rolled into a ditch following a crash in Auckland's north.

A boy on a bus that plunged into a ditch on Thursday "smashed his hand against the shattered glass of the doors" to help people get out safely, a student says.

Arabella Russell, 14, was sitting two rows from the front of the school bus when it crashed on Auckland's Dairy Flat Highway, just before 4pm.

After the bus went into the ditch, Arabella said a student who was at the back of the bus instructed everyone to get out.

"I stood up and I was stumbling around because I was very off-balance at that time," she said.

READ MORE: Residents fear Auckland's deadly highway

"He grabbed me by the jacket and helped me out of the bus – he smashed his hand against the shattered glass of the doors and pulled me out of the bus onto the grass.

AMY BAKER/STUFF The crash involved a bus and two other vehicles, police said.

"When I was getting out of the bus, I yelled at him to get the bus driver because he was in shock and so he turned around and tried to help the bus driver get out."

Both Arabella and her father, Peter Coleman, called the boy "the hero of the story" and wanted to track him down to thank him.

"It was only a pipe that was holding us from tipping into the creek. It was very unstable at the time and the whole bus was slowly leaning forward," Arabella said.

When the bus had to be stabilised, that made the experience even more "freaky", she said.

Alisha Hickling said her 13-year old daughter, Chloe, was sitting behind the driver when the crash occurred.

"I was talking to her on the phone and she was screaming 'the bus has crashed, help me'," Hickling said.

AMY BAKER/STUFF The windscreen of a school bus was badly damaged in a crash on Thursday afternoon.

Her daughter was "traumatised", Hickling said.

Glass was shattered all over Chloe's legs, and she was bleeding from multiple cuts.

"Chloe is scared to take the bus now."

AMY BAKER/STUFF Emergency services were on the scene for hours as they worked to clear the road.

Police said a bus and two other vehicles were involved in the crash, near the intersection with The Avenues.

No serious injuries had been reported, but three people – a student, the driver of the bus, and the driver of one of the other vehicles – had been taken to hospital as a precaution.

St John Ambulance spokeswoman Chrissy Hamilton said four ambulances had been sent to the scene.

AMY BAKER/STUFF Traffic was backed up through Albany following the crash.

Two of the patients had received moderate injuries, while one had received minor injuries, she said.

Ritchies Transport managing director Andrew Ritchie said earlier reports from St John Ambulance that the bus had rolled were incorrect.

The driver had swerved into a ditch to avoid a nose-to-tail crash on the road ahead, he said.​

The bus carried Albany Junior School and Albany Senior High School students, Hickling said.

The schools have been contacted for comment.

Reuben Alexander, a resident who lived in the apartments near where the crash occurred, said he heard a "loud smash".

"I come out and there's two cars here and a bus down the cliff," Alexander said.

There were crashes in the area all the time and it was "just a dangerous bit of road", Alexander said.