Fire crews from Launceston arrived at the scene about 2.30pm on Saturday to find that a fire in an external rubbish bin had extended to the roof space of a building.

The fire was soon contained, but not before serious damage was done.

In a statement, police said they had spoken to witnesses and reviewed CCTV images, and asked anyone with information to come forward.

"Tasmania Police detectives are investigating the cause of a fire which has caused significant damage to Riverside Primary School," the statement read.

"In addition to smoke and water damage to the property, the fire has damaged electrical cabling in the roof space, at an estimated $150,000."

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Information can be provided anonymously.

EARLIER:

A building fire at Riverside Primary School has been contained after multiple Triple Zero calls were made on Saturday afternoon.

Fire crews from Launceston arrived to find that a fire in an external rubbish bin had extended to the roof space of a building.

Tasmania Fire Service said the blaze was under control and that crews would remain at the site for a short time.

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