At least 73 people have been killed in a fire at a multistorey building in Johannesburg, South Africa’s biggest city, authorities said on Thursday. Another 52 people were injured in the blaze, which broke out before dawn, emergency services spokesman Robert Mulaudzi said. Some were suffering from smoke inhalation and were taken to hospital for treatment. At least seven children were among the dead and the toll is likely to increase, he said. The youngest victim was not yet two years old, Mr Mulaudzi added. It was not immediately clear what caused the fire, AFP reported. Having put out the flames, firefighters at the scene were on Thursday "busy with damping down", while search and recovery operations were continuing, Mr Mulaudzi told local broadcaster ENCA. "We are moving floor by floor conducting these body recoveries," he said. Mgcini Tshwaku, a member of the city's mayoral committee in charge of public safety, said candles used for lighting inside the building could have started the fire. Although the search and recovery team has recovered dozens of bodies, it was feared several people may still be trapped inside. “Over 20 years in the service, I’ve never come across something like this,” Mr Mulaudzi said. Authorities said the fire had been extinguished but smoke was still rising from windows of the blackened city centre building. Strings of sheets and other materials were hung out of some windows. It was not clear whether people used them to try to escape the fire or if they were trying to save their possessions. "Inside the building itself, there was a [security] gate, which was closed, so people couldn't get out," Mr Tshwaku said. "Many burnt bodies were found at that gate," he said. Mr Mulaudzi said homeless people had moved into the building without any formal lease agreements. He said that made it difficult to search the building. Witnesses estimated that there could have been as many as 200 people living in the building, including in the basement, which should have been used as a parking garage. Others estimated an even higher number of occupants. The building, which has been evacuated, is in a deprived area of what used to be the business district of South Africa's economic centre. City officials said 141 families were affected by the tragedy but could not say exactly how many people were in the building when the fire started. Many of the people inside were foreign citizens, the officials said. Fire engines and ambulances were parked outside the red-and-white building with burnt-out windows. The site has been cordoned off by police. Illegal occupation of disused buildings in the city centre is widespread, with many said to be under the control of criminal syndicates who collect rent from occupants. A witness said he saw people throwing babies from the burning building in an attempt to save them and that at least one man died when he jumped from a window on the third floor. Emergency crews expected to find more victims as they worked their way through the building.