Firefighters were battling a large blaze at an intermediate school in Hawera this morning.
Central Fire Service spokeswoman Jan Wills said 11 crews were called to the fire at Hawera Intermediate School, on South Rd, just before 6am.
She said the fire was "well involved" in a two-storey block when the crews arrived.
The building houses eight classrooms.
"All we know is it was well involved on arrival and all manpower is being utilised. Everybody on the scene is currently doing something.
"[It's] fairly large," she said.
It was too early to say whether it would be treated as suspicious, Ms Wills said.
The fire has been reported on social media, with @Debb63 tweeting: "Fire. Hawera Intermediate School" at 6.30am.
Flames and black smoke could be seen rising into the sky above the two-storey building.
A photo of the blaze on Facebook has prompted a number of responses from people in the community, commenting on how sad it was to see.
Hawera is the second-largest town in the Taranaki region, situated 75km south of New Plymouth.
Hawera Intermediate School is closed for the day because of the blaze.
The school posted a message on its Facebook page at 6.20am, stating it would update parents and students as soon as it could.
"Yes it is true our school is on fire," the post read."
Thanks to the awesome firefighters who are doing a great job. No school today for us. Updates as soon as we know."
A teacher at Turuturu School - a primary school about 3km away from Hawera Intermediate - has tweeted the fire was "devastating" to the community.
Sharon Honeyfield said: "Massive fire burning at Hawera Intermediate School in South Taranaki. Devastating for all."
Twitter user @steelbanks agreed: "The poor people from Hawera school. They'll be devastated."
Jody Timu-Kaea said the sound of fire engines rushing to the blaze had woken her up this morning.
"Woke up to sirens, fire alarms oh r.i.p Hawera Intermediate!" she wrote on Facebook.
An employee at Z petrol station in Hawera said he could see fire engines lining the street.
He did not know when the fire started or the cause of the blaze.
"I can see the fire engines but that's all I know," he said.
McDonalds employee Yvette Robinson said customers had been reported large flames and smoke this morning.
Hawera McDonalds is situated down the road from the school, right next to the fire station.
Ms Robinson said she heard the fire station alarms going off before 6am and fire engines rushing to the scene.
"Customers keep telling us it's really bad. I have a colleague that came in at 4.30am and there was nothing going on, so it must have happened after.
"We're next to the fire station and can see the brigades, we're quite close. It sounds pretty hectic."
Ms Robinson was not aware of any previous fires occurring at the school in the past.
A Hawera fire safety officer said asbestos had been found in the roof of the building which was ablaze.
Flames were still visible at Hawera Intermediate more than two hours after the first fire engine arrived at the scene.
The school field was full of fire appliances, with brigades from Hawera, Stratford and Eltham, as well as lots of bystanders.
Most of the school's teachers were silent as they watch their workplace smoulder.
The deputy principal said they were not allowed to talk to media at this point, but a statement would be released later.
Much of the second storey is completely gutted.
Student Rylee Gorham, 12, said the library was completely gone.
"I spend heaps of time there normally, now all our books are gone."
Aroha Kingi was almost in tears as she watches the building burn.
"My kids went here, they are at high school now. I just cant believe it. All the kids work, their art, their writing, poor kids. It had better not be arson. How could someone do this, destroy our kids place?"
Desmond Teawhe-Campbell, 7, and his brother Iosia, 6, were hanging out on the firemans pole in the playground after coming to see the fire with their father Desmond Campbell.
"It's awful, the flames were massive early on," he said.
A witness said the fire started in the library which is now completely destroyed.
Hawera Intermediate principal Craig Simpson said "a good cry in Manaia" helped as he made the drive from his home in Opunake this morning after hearing the news of the fire.
By the time he arrived, the blaze was still raging and staff and community members were already onsite.
The school had probably lost three-quarters of its buildings including classrooms, the library and the hall, he said.
"Thank goodness the admin block is OK," Mr Simpson said.
Board chair Mark Crawshaw said the school community was devastated by the fire.
He and Mr Simpson were both heartened by the immediate outpouring of support from the community, including the offering of temporary classrooms from other schools.
The school hopes to have students back in lessons by the end of this week.
The next step would be meeting with the Ministry of Education buildings team today to see how it can help.
A Ministry of Education trauma team would also talk with the school on how it could support staff and students.
The Fire Service was still working to make the school safe, Hawera Police Senior Sergeant Kyle Davie said.
Police would launch an investigation once the fire was completely out, he said.
"Police is currently keeping a cordon at the scene and once the fire has been put out and the area made safe, we will begin our investigation into what may have occurred. Until then we cannot comment," he said.
"We will certainly be actively working towards identifying who or what is responsible for the fire as soon as possible."
Anyone with information about the fire is urged to call anonymous hotline Crimestoppers on 0800 555 111.
Motorists are advised to take care around the area.