“There aren't the normal rats you see in the forest. They're as big as cats,” Benny Sagmo from the city planning office told TT.
The municipality has warned residents of the area to keep doors and windows closed to avoid letting the rats into their homes or giving them access to food. It also recommended making sure to use secure compost bins and avoid leaving rubbish behind after picnics in the park.
“We're appealing to everyone,” the municipality's environmental coordinator Kristin Eriksson said.
At the Trädet preschool children have been temporarily banned from eating or taking their naps outside.
“I decided that the children should sleep inside, because we can't risk rats jumping into the pushchairs,” headteacher Mia Löfgren told SVT Västernorrland.
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A private recycling centre is believed to be the cause behind the boom in rodents; the centre is in the process of moving, which has meant the rats' habitat has disappeared. Some of the animals may also be coming from the municipality's own recycling centre, situated in the same area of Johannedal.
On Wednesday, the municipality brought in a pest control firm to try to get rid of the creatures. Fifty traps have been set out, each of them capable of catching two rats, and the municipality is pondering using other methods on Thursday if the traps don't solve the problem.
“If we don't put a stop to it, they can get bigger and bigger. But I know we'll stop it, whatever the cost,” said Sagmo. “They've already spread out towards a residential area. Those who live there can't even have their front doors or balcony doors open. I've told pest control that we're going all in!”