The cause of the fire on Sunday night in Bohmte near Osnabrück remains unknown, but the building with a wooden roof was so badly damaged by the blaze that authorities fear it may collapse.
Three of the four victims found dead in the building had been identified by morning, police reported. Among them were two 71-year-olds and a 63-year-old. One of the dead was saved from the building still alive but later succumbed to severe burns.
Another victim was rescued from the burning house when he escaped to the roof and was rescued by a helicopter. He suffered smoke inhalation, authorities said.
Meanwhile another man and two fire fighters were injured in the fire.
The home was reportedly set up by the AWO organisation to aid homeless drug and alcohol addicts. Eleven residents were reportedly in the home when the fire broke out.