Several people were taken to hospital after a fire in a tent at the "Piteå dansar och ler" festival on Thursday afternoon, which Piteå-Tidningen was the first to report on.
A man in his 30s is seriously injured, according to Region Norrbotten. Two other people have sustained minor injuries.
The cause is believed to be a gas stove, says Felicia Grape at the rescue service.
The fire is said to have already been extinguished when the rescue service arrived at the scene.
The alarm about the fire came on Thursday afternoon.
The police have filed a report on work environment crime through negligence leading to bodily harm.
A man in his 50s with ties to the tent is suspected of the crime.
Corrected: An earlier version of the text contained incorrect information about how many people were injured.
