An explosion occurred in a store in the Södertälje district of Geneta on Monday.
Two teenagers have now been arrested, suspected of involvement in the incident.
The police received the alarm at around 20:00 on Monday evening. At that time, an object had been thrown into a store and detonated. According to P4 Stockholm, the police have confirmed that the object was a hand grenade.
A 16-year-old boy was arrested on Tuesday, suspected of, among other things, attempted murder and reckless endangerment.
The police write on their website that another person has been arrested in a "related case", suspected of serious weapons offenses and preparation for murder.
We have a 17-year-old and a 16-year-old arrested, suspected of involvement in this, says Max Åkerwall, deputy police area chief, to Sveriges Radio Ekot.
In connection with the explosion, a woman was injured and had to be taken to hospital by ambulance helicopter. According to the police, her injuries are not considered serious.
According to Aftonbladet, the explosion can be linked to previous violent incidents in Södertälje.
It's nothing I can confirm. But we're definitely looking into whether this has connections to recent incidents and how it can help us, says police press spokesperson Mats Eriksson to the newspaper.
On July 6, the police established a visitation zone in parts of Geneta and Västra Blombacka in Södertälje after a man was shot dead in Blombacka on July 2. The visitation zone was lifted on Friday.