Singh, however, denied he had been questioned by the CBI on Tuesday and claimed that it will be known in the coming days as to why "someone" was raking up this issue one and a half years after the deal.
"I have not been called by CBI today. Investigation will reveal that I am not involved and also the reasons for someone raking it up one and a half years after the alleged incident," he said in reply to an SMS sent for his reaction.
CBI sources, however, maintained that he and Rishi were questioned about some infirmities detected in their statements yesterday.
During the questioning session, Singh and Rishi denied having any kind of links with each other, they said.
The sources said the two Delhi-based businessmen and two executives of Vectra were also questioned in connection with the case and were asked about their association with the officials of the defence ministry.
The then Army Chief Gen (Retd) V K Singh had alleged that Singh offered him a bribe of Rs 14 crore in his office in September 2010 to clear the purchase of a tranche of 1,676 substandard Tatra BEML trucks, a matter he had reported to Defence Minister A K Antony.
After getting a formal complaint from the then army chief, CBI had initiated a preliminary enquiry in April.
Singh had refuted the allegations and also slapped a defamation case against Gen Singh.
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