The municipality is currently working on installing 10 digital rat traps in Södertälje's sewer system.
The method has previously been tested with a trap for a year and the results are good.
- These traps take at least 20 times more rats than those on the ground.
If you see a rat above ground, there are 20 more below ground, says Tomas Lindgren.
There are already about 30 electronic traps in five of Södertälje's parks Stadsparken, Turingelunden, Kvarnlunden, Brunnsängsfältet and Stationsparken.
The municipality has also put up new signs to remind people of the importance of not feeding birds or leaving rubbish on the ground, as it can feed the rats.
The clip below is from May 25 when SVT visited a school that reported that rats ran among the children in the schoolyard.
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Here at the school, the rats have been seen.
Play the video to hear more about the problem: "Been inside the yard".
Photo: Nada Razooq / SVT