A senior staff member from the nursery said the kids found capsules that were "strange and egg-shaped" and measured four centimetres in length.
"White powder came out from the packaging," the staff member told the Mitt i newspaper on Tuesday.
Once the capsules were discovered the children immediately left the scene and the police were alerted.
"You obviously get worried that they were able to find such things. It may well be something harmless but it could also be something that the children shouldn't try," said the head of the pre-school.
The police have kept tight-lipped about exactly what type of drugs the kids stumbled upon.
"Right now it is classified as serious drug offences," Niklas Kraft of the Norrorts police told the paper. "There are a lot of drugs worth a lot of money."
He added that he thought the drugs were in the forest to be out of reach of police. Police currently have no suspects in connection with the find.
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Last year the police made more than 34,000 drug seizures. Approximately half of those drug busts were for cannabis or cannabis resin.