It's not clear that caused the Monday crash.
A light rain was falling over most of Sao Paulo during the crash, but there were no reports of heavy downpours typical during the South American summer.
A spokesman for Brazil's air force says the aircraft that crashed was a Bell 206 helicopter that can carry up to seven passengers and a pilot.
It was being operated by as an air taxi. Sao Paulo has one of the world's largest private fleets of helicopters, used as a means of bypassing extremely congested roads.
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