In just a short time, nine hand grenades have been used in Malmö, though not all of them have detonated.
The newspaper Sydsvenskan reports that if someone throws a hand grenade and it doesn't explode then, it can lie hidden under a car or in a bush, for example.
"There's a big risk that there are several, but that have not exploded. The worst would be if a child finds a hand grenade and starts to play with it, that could end in catastrophe," says Göran Månsson, the chief of the national bomb protection unit in Malmö, to the newspaper.
The bomb unit has been called several times both this year and last year to deal with unexploded hand grenades that have been found, Månsson says.
Most of the grenades in Malmö come from the former Yugoslavia, and they are often old and can be rusty or oxidized, reports Sydsvenskan.
"The hand grenades can be taken from the battlefield or taken from dead soldiers by the local population," he says.