Rescue workers were combing through piles of concrete and glass Friday in an ongoing search for survivors from an apartment building explosion in southern Ukraine, but authorities said hope was waning as the death toll climbed to 27. Salvage teams have pulled 21 people out alive from the rubble since the five-story building collapsed Wednesday night in the Crimean peninsula resort of Yevpatoriya. It was unclear if other victims could still be buried in the wreckage. Authorities said 62 people were registered as living in the destroyed apartments, but could not say how many were in the building at the time of the blast. Ukraine held a day of national mourning Friday, with flags across the country lowered to half-mast. Entertainment events were canceled. Rescuers were using a construction crane to remove larger concrete blocks from the site, and were falling silent intermittently to listen for any cries of help. Television footage showed rescuers on Thursday pulling out a man, awake and alert but with bruises on his face, as rescue colleagues applauded. But finding others alive after two nights of temperatures at minus 6 degrees Celsius (21 degrees Fahrenheit) was increasingly unlikely, said spokesman Volodymyr Ivanov of the Crimean branch of the Emergency Situations Ministry. "There is very little hope," he said. The explosion caused the entire central section of the building to come down, exposing apartments on either side. As of Friday evening, 27 bodies had been recovered, including two children, officials said. Officials were considering several causes for the blast, including the explosion of oxygen canisters in the basement, Ivanov said. Neglect of safety precautions has led to frequent explosions in apartment buildings and public facilities in the ex-Soviet nations. Ukrainian President Viktor Yushchenko and Prime Minister Yulia Tymoshenko were in Yevpatoriya on Thursday to inspect rescue efforts and talk to survivors. Tymoshenko said survivors would be given free housing before year's end. Yushchenko thanked Russia for offering to send naval personnel to help with the rescue, but said they were not needed. Russia's NTV television reported that the remnants of the building would soon be torn down due to safety concerns. "We renovated the whole place, we installed new windows, and to leave it all?" resident Ivan Velnus said, struggling to hold back tears.