Security footage identified three children, whose names are now with police, Foster said. However, they are unknown to the principal.
"In the footage, we saw them arrive and then we saw them leave and as we saw them leave, we saw the smoke come out of the building.
The damaged building, called the Whanau Resource Room is used to house sports uniforms and equipment.
Despite no damage inside the room, Foster said they needed to make sure the uniforms had no smoke damage.
Today insurance assessors are expected to evaluate the damage.
It is understood about one-third of the roof was burnt, something which need to be fixed as soon as possible, Foster said.
However, they are also looking at ways to prevent another incident.
"We'll have to get together as a board and discuss whether we have lock our gates in the weekend at night when we leave to make sure no one comes into our school grounds."