The cause of a dramatic school bus blaze in Northland remains unknown.

The driver and 19 students escaped as the bus filled with smoke just before 4pm yesterday near Mangawhai.

Students evacuated through the driver’s side exit when the main doors failed to open.

Locals on Facebook said they were told via a text that the cause of the fire was a “mechanical issue”.

However, Fire and Emergency New Zealand said the cause of the blaze is currently undetermined.

A Fire and Emergency NZ spokesperson said the first crew from Mangawhai arrived at the fire, near the intersection with Carter Rd, just after 4pm.

A road was partially closed as crews battled the blaze, which was out by 5.10pm.

The father of a 13-year-old girl on board said the news came as a “shock”, especially with this being only the second week his daughter has taken the bus.

His daughter told him the doors wouldn’t open, and they had to climb out the driver’s side.

“Bit concerning that the doors wouldn’t open ... there should be an emergency over-ride,” the father said.

A school bus has caught fire in Mangawhai. Photo / Google Maps

“They pulled over, and the bus was filling with smoke. From what I’ve heard, [the driver] did a good job getting them all out.”

One local called the incident a “frightening sight”.

A Ritchies Transport Northland spokesperson said they were glad the incident ended safely.

“As is always the case in situations like this, the incident is now the subject of a thorough internal investigation bringing in independent expertise as required.”

Ritchies said given the investigation, it had no further comment to make.

People online have hailed the bus driver as a hero.

One woman posted on a Mangawhai Facebook community page that she was organising an appreciation gift for the driver, telling parents of the students who escaped to message her if they wanted to contribute.

Some commented saying although their child wasn’t on the bus that day, they would still contribute.

Another person said the driver sounded like he did an “amazing job”.