Update: Police now say the fire was caused by stray fireworks (SE) that landed on the mosque's roof. (h/t Snaphanen in comments)
The fire which damaged a building sometimes used as a mosque in Vänersborg, north of Gothenburg, was most likely started on purpose, according to police.
Police received a call around 9 pm and the fire was under control four hours later. The main damage to the building was caused by smoke and water leaks but police have no suspects so far, Swedish Radio News reports.