Transcript for Investigators still looking for cause of fire that toppled high-rise building

We turn overseas tonight, and to dramatic pictures, the fiery collapse of a high rise tower in Brazil. The stunning images of the raging fire, and then the building suddenly falling to the ground. The high rise was 'em tip, but dozens of families already made it their home. Tonight, several are missing, and here's ABC's Victor Oquendo. Reporter: It's the middle of the night when the fire erupts on the first floor, quickly consuming the entire high rise. Thick, black smoke spews out. Then, this horrifying image. The building comes crashing down. The dramatic collapse captured by bystanders. As fiery debris and smoke engulfs surrounding streets, officials say at least 50 families were living inside the 24-story building in Sao paolo, Brazil's largest city. The former federal police headquarters had been abandoned and occupied by squatters. This man says he went knocking door-to-door shouting, "Fire." At least one man confirmed dead. The fire department says he was clinging to a rope, talking to firefighters, but the building collapsed before they could save him. Tonight, a mother and her twin children are missing, and there could be more. The building still smoldering today. Rescuers seen going through the rubble in a desperate search for survivors. Officials are still looking for a cause. Rescuers say they won't use heavy equipment for at least three days with the hope of finding survivors. David? Victor, thank you. We turn next to the

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