A large-scale rescue operation was continuing Thursday evening at the site of a collapsed condominium block in Miami, where authorities said at least one person was killed, 10 injured and dozens more unaccounted for. Crews reported hearing noises from inside the rubble as they searched for survivors at the Champlain Towers South condo in Surfside, a 12-storey apartment block that came crashing down at about 1.30am. Authorities said they expected the number of deaths to rise, but would not be drawn on the number. On Thursday afternoon the Miami-Dade police chief, Alfredo Ramirez, said that 99 people remained missing, and that 53 condo residents were rescued or otherwise accounted for. The cause of the collapse was not known, he said, but an estimated 55 of the 130 apartments were affected. Police have launched a homicide inquiry, according to Sally Heyman, a county commissioner who represents Surfside. “It’s the unimaginable,” Daniella Levine Cava, the Miami-Dade mayor, said. “A massive search and rescue mission is under way. We are going to do everything we can possibly [do] to identify and rescue those who have been trapped in the rubble.” More than 80 fire-rescue crews attended the scene in Surfside, a small, oceanfront city just north of Miami Beach. Early video of the aftermath of the collapse showed a boy being pulled from the wreckage, one of 35 people rescued alive, the Miami-Dade commission said. “They brought dogs who can sniff for survivors in the rubble,” Eliana Salzhauer, a Surfside commissioner, told the Miami Herald. “They aren’t turning up very much. No one is celebrating anyone being pulled out.” Salzhauer confirmed earlier reports that recent construction work on the roof had taken place and said residents told her a building inspector had visited the property on Wednesday. But she said it was too soon to speculate on the likely cause. Jimmy Patronis, a Florida cabinet member and the state’s fire marshal, told reporters that crews had heard noises as they sifted through the wreckage. “The rescuers are hearing sounds from the rubble. It’s kind of hit or miss. You get into the zone where you are so passionate and so focused and so determined to make sure you are doing everything possible to save a life in an event like this,” he said. Earlier, Frank Rollason, the director of the county’s emergency management department, said workers believed that they had rescued all reachable survivors. “Everybody who is alive is out of the building,” he told the Herald. In one of the first rescues, he said, workers saved a trapped mother and child, although the mother’s leg had to be amputated to free her. Other terrified residents were plucked from their shattered balconies by rescue workers with cherry pickers, after finding escape routes blocked. The Florida governor, Ron DeSantis, visited the scene and spoke with survivors and rescue teams after cutting short an event in Tampa. “It’s a tragic day,” he said at an afternoon press briefing. “The TV doesn’t do it justice. It is really, really traumatic to see the collapse of a massive structure like that.” The governor said state emergency management officials were present and that engineers would investigate the cause of the collapse when it was safe to enter the site. “You’re not going to have those answers immediately,” he said. Levine Cava, the Miami-Dade mayor, said in a tweet that Joe Biden had called to lend support. The US president, she said, “offered the full support of the federal gov[ernment] to help our community during this difficult time”. Biden said he was waiting for DeSantis to issue a state of emergency before federal assistance could be given. “We are ready to move from the federal resources immediately, if in fact we’re asked,” he said. “But we can’t go in and do it. Whatever help you want that the federal government can provide, we’re waiting, just ask us, we’ll be there.” The Surfside mayor, Charles Burkett, said he understood from the building manager that the condo block was “substantially full” of residents mostly sleeping at the time of the collapse. “The building is literally pancaked,” Burkett said at the press conference. “That’s heartbreaking because it doesn’t mean to me that we are going to be as successful as we wanted to be in finding people alive.” Meanwhile, concerned friends of those unaccounted for went on social media to plead for information. Witnesses gave harrowing accounts of the moments following the collapse. “I could hear somebody yelling, screaming. I could hear by the voice it was a little boy, I saw an arm sticking out of the debris,” Nicholas Balboa, who lives nearby, told CNN. He said the boy and a person with him were trying to climb out but could not lift the heavy rubble. The boy was screaming, “Don’t leave me, don’t leave me,” Balboa said. Families with children in pajamas were seen arriving at a Red Cross reunification facility set up for survivors at a nearby community center. The group was arranging hotels for displaced condo residents. The building that collapsed was a southern tower of the condominium development, said Rollason, the director of the county’s emergency management department. Residents of the other towers were evacuated and engineers were inspecting the buildings for safety. The collapse sent up a cloud of debris, coating cars up to two blocks away with a light layer of dust. Photos and video from the scene show the collapse affected half the tower. Piles of rubble and debris surrounded the area just outside the building. Unconfirmed reports said that maintenance work had been taking place on the roof of the building that collapsed. The building’s address is 8777 Collins Avenue, according to Surfside police. The sea-view condo development was built in 1981 in the south-east corner of Surfside, on the beach and includes more than 100 units. It had a few two-bedroom units on the market, with asking prices of $600,000 (£429,500) to $700,000, an internet search shows. The area is a mix of new and old apartments, houses, condominiums and hotels, with restaurants and stores serving an international combination of residents and tourists.