The Norbotten-Kurrien newspaper said the informant told the paper that the tall, leafy plants were growing at the Floras Knoll park, The Local reported.

"There's cannabis growing on Floras Knoll," the tipster said. "I'm totally sure. I've grown it myself."

Norbotten-Kurrien said police initially claimed the plants were likely a "harmless hemp agrimony plant," but a Jamacian expert visiting the city, Kent King, said he had no doubt that the plants were cannabis.

"It is ganja," he said. "I grew up with this. I'm one hundred percent sure."

The plants tested positive for the active chemical in marijuana.

"This is definitively cannabis. We don't know how strong, but it is cannabis," a narcotics division officer said.