A fire in a toilet at Waitaki Boys' High School is being treated as arson by Oamaru police, who were called there yesterday, along with two units from the Oamaru Fire Brigade.
Toilet paper set alight on a cistern burnt the lid, sides and seat of a toilet.
Another two attempts to set toilets alight were also discovered, although they only caused scorch marks on plastic cisterns.
''It appeared a cigarette lighter had been held to the plastic,'' Oamaru Fire Chief Steve Couper said.
The school was evacuated during the fire, which was reported at 1.10pm, and the brigade's portable fan was used to clear smoke from the corridor before pupils could return.
Mr Couper said Fire Safety had been notified of the fire, but was not investigating because police were involved.
Const Dowling said police were doing forensic tests on ''a couple of items'' from the third fire.
School commissioner Nicola Hornsey and rector Paul Jackson were involved in interviews yesterday and did not respond to questions from the Otago Daily Times.
