The fire broke out in a kitchen in the Rosengauße neighborhood of Berlin on July 8, 2016, after a party at a rented apartment complex.
A total of 23 people were killed and more than 200 injured, according to authorities.
The building had been rented out to a company owned by a family from Hamburg, but was not registered as a hotel.
The blaze was started in a bedroom in the house, the Rosenskirche, which was rented by a company from Hamburg.
It caught fire on a fire escape and then spread to the third floor.
A local police officer was on the second floor when the fire started.
At least 30 firefighters were on site and at least 10 of them were treated for smoke inhalation, according the Interior Ministry.
As the fire raged, there were also reports of smoke coming from the roof of a nearby building.
Authorities ordered a temporary halt to all parties, and the police cordoned off the area.
The city has been without power for days, and some roads have been closed.
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The fire broke in a backyard in the residence of a member of the Hamburg family, which also owns the apartment building.
Authorities said the apartment had been used as a restaurant.
Investigators believe the fire originated from the kitchen in a room belonging to the Hamburgs.
One of the apartment’s tenants was in the kitchen and reported that the fire had started from his bedroom, according a Hamburg news website.
Some of the apartments in the area have had problems with heat.
An official with the Hamburg police told the Associated Press news agency that it was unclear how the fire began.
Police are looking into whether any of the victims in the apartment were able to escape.
More to come.