A family building fire in southwest Germany resulted in nine people killed, five of them being children, police said Monday.

Firefighters were called to the blaze at 4:21 local time Sunday at a building in the German city of Ludwigshafen, which celebrated the first day of Carnival. A parade of costumed Carnival-goers had just passed near the house in the city center before the fire began.

The fire engulfed the stairwell of the four-story building, reducing the wooden staircase to ash and forcing panicking residents to crowd to windows and balconies and leap to the ground. Firefighters who made their way into an upper floor rescued two children who were cowering behind a couch.

Police found eight bodies in the building and one woman, believed to be pregnant died in a hospital after the fire, police representative Simone Eisenbarth said, according to the Associated Press.

“Unfortunately, we cannot exclude further victims,” she said.

Fifty-two people, mostly Turkish citizens, were registered as living in the building, which authorities said was in danger of collapse. However, police could not give an exact number of dead or injured people. Other people were believed to have been watching a carnival procession from the building.

The cause of the fire was not clear and the victims had not yet been identified, Eisenbarth said. Police fear the fire may have been started deliberately, possibly by neo-Nazis who targeted the apartment block because of its largely Turkish population.