Fire crews are battling a "ferocious" blaze at a central Auckland school.

Aucklanders from the North Shore and western suburbs can see smoke billowing across the city after the fire broke out at Ponsonby Intermediate School.

The fire is in the school's techdome which is where art and textiles classes are held.

Police have blocked off nearby streets and ambulance staff are on the scene. It is unclear if anyone is injured. It is believed the fire started shortly after 4pm.

A fire has broken out at Ponsonby Intermediate in central Auckland. Photo / Dean Purcell

Duncan Shand of the nearby creative agency YoungShand said he saw flames leaping 30 feet in the air.

"It was ferocious," he said.

"It was out of control."

He said the fire was coming from the back of the school and appeared to be confined to one block.

"That school block is completely gone.

"There was lots of stuff dropping off."

He said once fire crews arrived the fire was under control pretty quickly.

"The whole building was up in flames," Shand said.

Smoke billowed over the central city as fire crews battled the blaze at Ponsonby Intermediate. Photo / supplied

Year 8 student, Maddie Reece, told the blaze was scary:

"I graduate in 2 days," she said.

Iris Archer is also in year 8. She says it is pretty bad as it looks like they will have to rebuild the classroom.

There is lots of tech equipment in the rooms.