P4 Jönköping has previously reported that the 16-year-old boy is suspected of, among other things, attempted murder. The Danish police do not want to comment on the exact crime suspicion.
Three more people have been detained since earlier for suspected involvement.
One of them is a 25-year-old Swedish citizen who was arrested a week ago with two hand grenades in the Tingbjerg area of Copenhagen. He is suspected of planning an explosion in Copenhagen, which failed because he was caught by the police.
A 31-year-old Danish man with ties to the gang criminal environment is suspected of having handed over the hand grenades to the Swedish 25-year-old. He is also suspected of having paid the Swede, arranged a hotel room, and acted as a chauffeur.
On Friday, a 25-year-old Danish gang member was also detained for suspected involvement. According to the prosecutor, he made his apartment available to the Swede and helped him order a taxi.
On Wednesday, Denmark's Minister of Justice Peter Hummelgaard (S) and Sweden's Minister of Justice Gunnar Strömmer (M) will meet in Copenhagen due to the many recent crimes with Swedish connections in Denmark.