Widening the scope of its investigations into irregularities involving defence PSU BEML Ltd, CBI has sought the defence ministry’s sanction to begin a corruption probe against its chairman and MD V R S Natarajan. CBI today questioned Ravi Rishi, chairman of the Vectra Group, in connection with BEML’s Rs 5,000 crore deal with Czech truckmaker Tatra, the company in which Vectra has a major stake.