Investigators said 15 to 20 people were attending midday prayers Thursday at a Somali group's mosque on the ground floor of a residential building in Eskilstuna when the flames erupted.
Five people were hospitalized with injuries including smoke inhalation and lacerations.
"Two suffer from smoke inhalation, two have cuts and bruises and one has a fracture," police spokesman Lars Franzell told reporters.
"A witness saw somebody throw an object through the window of the building, which serves as a mosque, after which a violent fire began," Franzell said.
Franzell said the incident is being investigated as arson, but no arrests had been made as of Thursday afternoon.
Police said they were evacuating the the apartments above the mosque and residents were being taken to emergency accommodations in a nearby youth center.
The Department of Public Safety was first on the scene, but wildlife officials weren't far behind. On the move since Monday, the black bear retreated to a suburban backyard after being hit by a tranquilizer dart at roughly five o'clock in the morning on Thursday. The homeowner wasn't home at the time.
Though the bear sports brown fur, it is a black bear -- a species that assumes a range of colors and is generally less aggressive toward and afraid of humans. The bear is between two and three years old and will be evaluated by a biologist before it's determined whether to release the bear back into the wild or house it at a rehabilitation facility.