Local authorities reported the victims include the business tycoon Celso Silveira Mello Filho, his wife Maria Luiza Meneghel, his three children, the pilot Celso Carloni and co-pilot Giovani Gulo.
Piracicaba Municipal Government said the accident happened 15 seconds after the plane left the Pedro Morganti Municipal Airport. The aircraft crashed into a forest area near the Technology College of Sao Paulo, setting off an explosion and fire.
The cause of the accident is being investigated by authorities.
Celso Silveira Mello Filho was a shareholder of Cosan, one of Brazil's largest biofuel producers.