The fire started in the early hours of the morning. Two adults and a toddler managed to escape from the inferno, and were taken to hospital.
One eyewitness said that the three survivors had suffered serious burns and smoke poisoning, online newspaper Blick reported.
Fire fighters searched the surrounding area and woods in search of the missing individuals, but none of the three were found.
Two girls, aged four and eight, and an elderly woman are missing, sources told Blick.
Fire fighters were prevented from entering the house for several hours due to the intensity of the flames.
Police have confirmed that they will release further information later on Monday.
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