BERLIN (AP) — Four people were seriously hurt in an overnight fire at a hospital in Berlin, including a patient who sustained life-threatening injuries, authorities said Monday. A man was detained in connection with the blaze.

The fire on the third floor of the Klinikum am Urban in the German capital was extinguished early Monday morning, the fire service said. Three patients and a nurse were seriously injured, among them a patient who got stuck in an elevator and whose life was in danger.

Forty people were evacuated as smoke spread through the building.

Firefighters said the blaze appeared to have started with burning beds in a corridor, but it wasn't immediately clear how they caught fire, German news agency dpa reported. Police said a man was arrested and arson couldn't be ruled out.