Officials said few people involved in creating an overseas firm with Mitchel have been called by the agency to record their statements under the provisions of the Prevention of Money Laundering Act (PMLA) this week.
The agency, sources said, wants to understand the "financial relationship" of at least three people who had created an offshore entity with Mitchel, approximately around the same time when the 12 choppers deal was being finalised and was in final stages of execution.
He is amongst the three alleged middle men being probed in the case by the ED and CBI both.
ED had registered a PMLA case in this regard in 2014 and named 21 people including former Indian Air Force Chief S P Tyagi in its money laundering FIR.
It had also arrested Delhi-based businessman Gautam Khaitan and had also filed a charge sheet last year.