The bodies of three people have been recovered in Brazil by rescue workers searching through rubble after the collapse of two high-rise office buildings in Rio de Janeiro. Officials say that at least 19 people remain missing, while a further six were taken to hospital. City Mayor Eduardo Paes said current investigations were focusing on structural problems. The buildings, one of which was 20 storeys, collapsed late on Wednesday. Mr Paes discounted speculation that a gas explosion could have caused the collapse. The buildings, which were respectively 10 and 20 storeys high and were located near the Municipal Theatre and the headquarters of oil giant Petrobras, crushed a four-storey construction site on their way down. Dozens of emergency workers attended the scene and police cordoned off the area. Electricity to the street has been cut off for safety reasons. Allesandro da Silva Fonseca told AFP he had been briefly trapped in a lift with five construction workers after they tried to escape. He said he had almost suffocated because of the dust. "I was out of air. I could not breathe," he said. Hugh Oliver, who was in the area when the collapse happened, told the BBC the situation was surreal. "The city quickly filled with rescue vehicles and there was a lot of helicopter activity. The dust cloud hung around for a long time," he said. Fire Department spokesman Moises Torres said that he had hopes of finding people alive, the news agency AFP reported. Luiz Cosenza, a building inspector with Rio de Janeiro's Regional Council of Engineering told Brazil's Globo televison network that he feared illegal projects could have been a factor, AFP reported. Mr Cosenza said: "Two projects were happening in the building, on the 16th floor. They were illegal works - they were not registered with the council." Mr Oliver said he was not surprised by the falling building and said: "The infrastructure is poor - only areas such as Barra de Tijuca are modern and well regulated, but behind the main streets in the centre of Rio there are crumbling dirty sidestreets where safety is not the top priority." The incident comes a little over three months after a suspected gas explosion at a restaurant in the city left three people dead. Concerns have been raised about the state of Rio de Janeiro's infrastructure as Brazil prepares to host football's World Cup in 2014 and the Olympic Games two years later.