Indian authorities filed a criminal case against the firm and its parent company Finmeccanica in March 2013 officials said.
The alleged scandal came to light after Finmeccanica's chief Giuseppe Orsi was arrested in Milan in 2013.
The Italian authorities said they had been investigating him for bribery and embezzlement for several months.Both Tyagi and Mr Orsi have denied any wrongdoing.
The luxury helicopters were intended to carry the Indian president, prime minister and other VIPs.
India's defence ministry cancelled the $753m (£597m) 12-helicopter deal in 2014, after announcing that it would carry out its own investigation into the matter.
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