'Could hear windows cracking': Fire destroys Auckland college classrooms

North Shore's Long Bay College is closed for the day after a fire tore through the school's art and technology block.

The fire started about 2.30am on Friday and by the time firefighters arrived the block was well alight.

School principal Russell Brooke confirmed on the college's Facebook page it would be closed on Friday.

Year 12 student Anastasia Zaikina, who lives near the college, told 1 News she woke up to the smell of smoke.

"You could hear the windows cracking and wood falling," she said.

"I’ve never seen anything like it."

A fire has destroyed the technology block at Long Bay College. Photo: Supplied

The Fire Service's assistant area commander John Booth said the fire was well alight when crews arrived.

The fire was still burning more than three hours after it was reported but under control, says Fire Service northern communications centre shift manager Jarron Phillips.

Around 50 firefighters and 13 appliances were called to the blaze.

An investigator would be at the scene later on Friday to try to determine the cause of the fire.

- With NZN