Fire crews said the cause of the fire was suspicious because of its size and the way it spread so quickly to four buildings.

Police said entry alarms sounded at the school grounds at 3.05am, before a member of the public telephoned triple zero and alerted police and fire crews.

At least one year 4 classroom, several year 3 classrooms and a mixed year 2 and 3 building were burnt in the blaze, which broke out just before 3am on the Pashen Street grounds.

One of the school’s original buildings was destroyed.

More than 50 firefighters fought the fire for more than two hours.

Officers were investigating if Morningside State School had security cameras.

“The Department of Education, police and fire emergency services advise the Morningside State School grounds are unlikely to be available for the rest of this week as they continue investigations and work to make the site safe,” an Education Queensland spokeswoman said in a statement.

“Thanks to the generosity of the Balmoral State High School community, all Morningside State School staff and students will be relocated to Balmoral State High School from [Wednesday] for the rest of this week.”

Balmoral State High School is on the corner of Thynne Street and Lytton Road at Balmoral.

Morningside staff and students would be “working as much to their normal program as possible” for the rest of the week, the spokeswoman said.

“There will be extra staff on hand to assist students at the high school campus and ensure they feel well supported and welcomed,” she said.

The spokeswoman said teachers wanted to have students back into the learning cycle as quickly as possible.

“We are working to get students back to learning as soon as possible and to minimise disruption to their school programs,” she said.

“Parents and the community will be kept updated and we will continue to work with the Morningside State School community to ensure children’s learning is impacted as little as possible."

Year 4 student Keenan Turner and her mother Sophie walked from their nearby home because they could not believe their school had been damaged.

"It's a little bit not real, that's why we had to come for a walk and see it for ourselves," Ms Turner said.

“We could smell smoke from around the corner at our house."

School chaplain Grant Lea said his wife attended the school from years 1 to 7.

"She was pretty devastated. It affects everybody that's been involved in the school community, whether it's the kids who are here now, the teachers, staff or past students," he said.

The school was declared a crime scene, with police and fire investigators and forensic teams scouring the burnt-out buildings.

"Due to the density of the population here, we hope people saw something and investigators will be door-knocking the area," Inspector Jeff Coote said.

Bulimba MP Di Farmer told state Parliament on Tuesday morning the fire had shocked the community.

“If you had seen the outpouring of emotion this morning at Morningside State School in my electorate, where three (sic) buildings were devastated by fire, you would know the kind of connection I mean,” Ms Farmer said.

“I want to give a big shout-out to everyone from that school community and say thank you to all of the fire and emergency services personnel who did so much to contain the site and support the school community.”