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.
"The CAG report and Ministry of Defence release on the VVIP helicopter deal last year clearly refutes the charges levelled against us by CBI," he added.
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.
A case was registered by CBI against former IAF chief Tyagi and 12 others, including his cousins, for alleged cheating, corruption and criminal conspiracy in the Rs 3,600 crore VVIP helicopter deal, in which Rs 360 crore is alleged to have been paid as kickbacks.
The former IAF chief has refuted the allegations against him.
The questioning of the Tyagi brothers became necessary after Haschke alleged that he had paid money to them for engineering works at IDS Chandigarh, footing rent and meeting administrative expenses in India.
They were questioned last year in the case and had denied any wrongdoing.
CBI has alleged in its FIR that Haschke, through his Tunisia-based company, Gordian Services Sarl, entered into several consultancy contracts with AgustaWestland from 2004-05 onwards and, "almost on a back-to-back basis he also made consultancy contracts with the Tyagi brothers".
Under the cover of these contracts, Haschke is alleged to have sent Euro 1.26 lakh (about Rs 1.06 crore) and Euro 2 lakh (about Rs.1.68 crore) to the Tyagi brothers.
"Besides these two remittances, the Tyagi brothers also received some unquantified sum of money from the middlemen (Haschke and another, Carlo Gerosa).
"The inflow of remittances to Tyagi brothers and softening of IAF's stand on service ceiling of the helicopter closely match in terms of time," the FIR claimed.
The allegation against the former Air Chief is that he reduced the height of the VVIP helicopters so that AgustaWestland could be included in the bids.
The decision was taken in consultation with the Special Protection Group and other top officials of the Prime Minister's Office, but the agency did not get permission to question either MK Narayanan or BV Wanchoo, the governors of West Bengal and Goa, respectively.
While Narayanan was the National Security Adviser, Wancho had been the head of SPG at the time.
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