BUZZ-Petroleo Brasileiro Petrobras SA: Fire at Sao Paulo refinery
** Brazil's state-run oil company's U.S.-listed shares down 3.3 pct at $17.04
** Fire at refinery operated by company left six workers injured in Sao Paulo state on Thursday
** Company says fire is under control and operations are continuing normally
** Petroleum workers' union has warned that worker safety conditions at company are deteriorating
** Up to Thursday's close, stock had risen about 28 pct this year
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