BERLIN — Three patients were killed and many people were injured in a fire that broke out overnight at a hospital in the German city of Hamburg, authorities said Sunday. Another patient was detained on suspicion of starting the blaze.

Firefighters were alerted to the fire at the hospital, the Marienkrankenhaus, shortly after midnight. It broke out in a room in the geriatric ward, on the ground floor of the building, and spread to the facade of the floor above. Smoke spread across the building’s four floors, German news agency dpa reported.

The three people who died were men aged 84, 85 and 87, police said in a statement. Another 34 people were injured, one of whom was in a life-threatening condition.

A section of the hospital had to be evacuated. Injured patients were treated mostly at the hospital itself, though two were taken to nearby clinics. The fire was extinguished within about 20 minutes.

Later Sunday, police said witness interviews suggested that a 72-year-old patient may have set the fire. He was detained on suspicion of arson.

— The Associated Press