KAMIEN POMORSKI, Poland (AP) âÄî Survivors of a fire that killed 21 people at a three-story shelter for homeless families in Poland on Monday described a fast-moving inferno that forced some to jump from windows into trees. Six of the victims were children and another 20 people were injured, most of whom sustained broken bones after leaping from the building to escape the blaze in the northwestern city of Kamien Pomorski. Poland’s president, meanwhile, raised questions about whether the building met fire regulations. He suggested flammable construction material may have contributed to the fire’s speed and intensity. Survivor accounts appeared to support that. “I couldn’t breathe, so I opened the window and looked out, and the door was on fire because it was essentially made of paper,” a survivor told reporters at the scene in footage shown on TVN24 television. “I put my pants on and boots, and a friend gave me a jacket, and there wasn’t any more time because it was burning like a torch. Some people jumped into the trees,” the unidentified middle-aged man said. The cause of the fire, which began around 1 a.m. (2300 GMT Sunday), was under investigation. The building is owned by the county government. “If the building burns at that fast a rate, and if nobody poured gasoline over the entire building and set it alight on purpose âÄî and that theory doesn’t exist right now âÄî then there must have been some fundamental flaw in the construction,” President Lech Kaczynski told reporters after visiting the site. Police and fire investigators continued to comb through the building’s smoldering shell late Monday in search of clues. The first floor was built of concrete and the top two floors had a metal frame. But officials said the walls appeared to be made from a highly flammable material. Footage broadcast on TVN24 television taken when firefighters first arrived showed the building engulfed in flames. Later video showed firefighters picking through the building’s blackened, gutted shell with axes. It was not immediately clear what alarm systems the building had. The building was unlikely to have had smoke detectors, but likely did have a sprinkler system, national fire department spokesman Pawel Fratczak said. Fratczak also said it was Poland’s deadliest fire since 55 people were killed in an October 1980 blaze at a psychiatric hospital in Gorna Grupa in central Poland. Police said the death toll could still rise because 11 people are unaccounted for. There were 77 people registered as residents in the building at the time of the blaze. But Fratczak threw doubt onto that figure, saying firefighters “searched all three floors and everything left in them, such as burnt furniture, and we didn’t find any remains.” Prosecutors said they would use DNA tests to identify the charred bodies of those who perished. Two of the injured were being treated for burns, including an 8-month-old baby. The injuries were not considered life-threatening. “I’m in shock. The most important thing is that we’re alive and that the kids are alive,” a woman lying in a hospital bed with burns visible on her face told TVN24 through tears. “I’m just worried what happens now. We lost everything. We have nothing. I hope there is somebody who will help not only us, but everyone who has suffered from this because this is truly a tragedy.” Prime Minister Donald Tusk inspected the damage early Monday, and promised aid for those who escaped the blaze. Many of the residents had been living at the shelter for a long time as they waited for a permanent apartment in Poland’s crowded public housing network. “The help will be full and will ensure the housing needs of those who survived this disaster,” Tusk told reporters in front of the still smoking building. “The most important thing is to help those who survived.” The building in Kamien Pomorksi, about 370 miles (600 kilometers) northwest of Warsaw and near the Baltic Sea coast, originally served as a bare-bones hotel for workers in the region’s gas fields. Ownership of the building was transferred to the county government a few years ago. The president declared three days of national mourning to start at midnight in memory of those who died.