At least 21 people have been killed in a fire at a hostel for homeless people in north-western Poland, officials say. Another 20 were injured in the blaze in the town of Kamien Pomorski, 60km (37 miles) east of the border with Germany, which began in the middle of the night. Many of the injuries were sustained as residents jumped from upper floors of the three-storey building. At least 77 people were registered at the hostel, waiting for the local authority to provide them with housing. Emergency teams are now sifting through the wreckage of the building. The cause of the blaze is not yet known. Prime Minister Donald Tusk broke off his Easter holiday to fly to Kamien Pomorski early on Monday to inspect the damage, determine what help was needed, and express his condolences. "The help will be full and will ensure the housing needs of those who survived this disaster," Mr Tusk told reporters at the scene. President Lech Kaczynski has meanwhile declared three days of national morning to start at midnight, and is also to visit the town. 'Too late' The fire broke out in the three-storey hostel at around 0100 (2300 GMT on Sunday) and spread rapidly. Witnesses said the building went up like a torch. "The fire spread at an incredible speed," Daniel Kopalinski, a member of the local emergency services told TVN24. "Firefighters had to catch children thrown through windows by their parents," he added. One of the survivors said those inside were forced to jump because the rescuers' ladders had only reached the first floor. "I yelled to my sister on the second floor 'Jump, I will catch you', but she didn't. Then it was too late," Dariusz Janyszko told TVP. One of the injured is in a serious condition. Many, including one child, are suffering from burns and the effects of smoke inhalation. Officials said not all of those registered as residents of the hostel had yet been accounted for, and that the death toll might still rise. "It will take a couple of hours to search the entire site," fire service spokesman Pawel Fratczak said after the blaze was extinguished. Mr Fratczak said it would be difficult to identify many of the victims quickly because their bodies had been so badly burned. Source: BBC