Over a hundred students and at least ten teachers at a school in Holmsund reported sick after falling ill with some form of stomach complaint on Wednesday night.
In the pre-school class, as many as 71 out of 99 children stayed home from school.
According to Region Västerbotten's infection control doctor Gunilla Persson, tests now show that the school was hit by an outbreak of winter vomiting disease, reports Aftonbladet.
It's an unusual situation. There had been some symptoms at the school earlier, but now that so many people got sick at the same time, we believe it probably came via the cafeteria, says Gunilla Persson to the newspaper.
She says that those who got sick have recovered and that the school has taken measures with food handling and cleaning.