CBI sources said Julie and Docsa Tyagi have been quizzed on their alleged association with European middlemen Carlo Gerosa and Guido Haschkhe who have been accused by the Italian investigators for payment of illegal gratification to swing the deal in favour of AgustaWestland.
The sources said agency has already questioned executives of Indian arms of Aeromatrix and IDS Infotech--companies through which alleged bribe was routed from Mauritius and Tunisia in the garb of payments for engineering contracts.
It had claimed that Haschkhe and Gerosa, through the Tyagi brothers, managed to change the tender details, modifying the 'operational ceiling' from 18,000 feet to 15,000 feet altitude, thus making AgustaWestland eligible to take part in the tender process.
The report also said that the duo managed to introduce a comparative flight trial with non-functional engine, thus facilitating AgustaWestland helicopters, the only ones which had three engines, swinging the deal in its favour.
The former Air Chief and his three cousins have denied the allegations.