Sources said that the agency has recently questioned Sanjeev alias Julie, Rajeev alias Docsa and Sandeep in connection with the claims made by Haschke.
"What I told CBI is that we have absolutely nothing to do with the deal and all supporting documents have been given to CBI," Sanjeev Tyagi told PTI when asked to comment on his examination.
"We are cooperating with CBI and went to them every time we were called," he said.
Sources said that Haschke, who was questioned first by Defence Ministry officials and then by CBI, had told the probe agency that money was paid to the Tyagi brothers for the engineering works and meeting other administrative requirements in India.
Arrested in Switzerland in September last year and later extradited to Italy to face trial, Haschke has denied that he had ever met the former IAF Chief or handed over any money to him to clear the VVIP helicopter deal in favour of AgustaWestland.