Fire destroyed a five-storey residential building with around 50 apartments in the western German city of Essen on Monday, injuring at least three people.
Fire department spokesperson Christoph Risse said the injured had been taken to hospital suffering from smoke inhalation. He said he was "cautiously optimistic" that everyone else had been able to leave the building.
Residents raised the alarm at 2:15 a.m. (0115 GMT). The fire had spread at high speed over a large area of the building when firefighters reached the scene, Risse told reporters.
Firefighters were seen hosing down the still-smouldering building.
"The difficulty is that we can only fight the fire from the outside because we cannot enter the apartments yet. So the operation continues, and only later will we be able to check the apartments inside," he said.
Essen police are investigating the cause of the fire, a spokesperson said.
(Additional reporting by Zuzanna Szymanska; Editing by Miranda Murray and Janet Lawrence)