UPDATE 3-Brazil's Schahin says 28 units file for bankruptcy protection
April 17, 2015 at 19:07 PM EDT
SAO PAULO, April 17 (Reuters) - Twenty-eight units of Brazilian engineering firm Grupo Schahin filed for bankruptcy protection and fired 2,500 workers on Friday as a corruption scandal at key client Petróleo Brasileiro SA hampered efforts to refinance up to 6.5 billion reais ($2.1 billion) in debt.