Police are speaking to a person in relation to a suspicious fire at Kaiapoi North School in the early hours of yesterday morning..
The fire, which started around 2am, caused significant damage to a classroom block at the school.
"It was a real shock to get the call...that the school was on fire," principal Jason Miles told 1 NEWS yesterday, explaining that he hoped to have the block demolished today so it would be safe for the students to return on Monday.
"We're just devastated," he said. "The children's work for the year is all lost, the teacher resources. There's a lot of emotion around that.
"We're upset, and then we're angry...We will get through it, but we're disappointed and devastated."
Police earlier released a photo of an unidentified man they wanted to speak to over the fire.
After locating the person of interest police say they are not looking for anyone else in relation to the incident and the case will be referred to Youth Aid.