About 25 people were in hospital after an explosion at a block of flats in the Swedish city of Gothenburg early on Tuesday, according to local reports.
Police said they had opened an investigation but had no suspects at the time. The fire service said there was no gas pipeline in the house.
At least three of those taken to hospital were seriously injured, Gotesborgs-Posten, a local paper, reported. The local hospital said three over-60s women were seriously injured.
The fire service said 15 units were on the scene. Eleven ambulances were reported on the scene.
Emergency services said they were working to evacuate people and put out fires inside. A spokesperson said several hundred people had been evacuated from the vicinity.
“It's awkward. There are at least three stairwells that are affected,” said Lotta Molander of the Greater Gothenburg Fire and Rescue Service.
The fire service said it was alerted to the explosion just before 5am. A nearby resident told the local paper she was awoken at 4.30am by a loud bang.
The immediate cause of the explosion and fire was unclear. The Nordic country has contended with surging gang crime in recent years, with rival groups employing explosives and firearms to settle scores.
