CBI sources claimed Singh and Rishi were confronted with each other as some infirmities were detected in their statements given yesterday.
The duo denied having any business links with each other during the questioning, they said.
The sources said the two businessmen and two executives of Vectra were also asked about their association with the officials of the Defence Ministry.
They claimed that the CBI suspected alleged association between Tejinder Singh and Rishi during the probe of a separate case related to Abhishek Verma, another arms dealer facing a CBI probe in several cases.
The sources said during the questioning of Verma and Tejinder Singh in the case, the agency got some information about latter's dealing with arms lobbyists which helped it to conclude that there was enough material to register a regular case on the basis of the then army chief's complaint.
Gen (Retd) V K Singh had alleged that Tejinder Singh offered him a bribe of Rs 14 crore in his office in September 2010 to clear the purchase of tranche of 1,676 substandard Tatra BEML trucks, a matter he had reported to Defence Minister A K Antony.
More From This Section
After getting a formal complaint from the former army chief, CBI had initiated a preliminary enquiry in April.
Tejinder Singh had refuted the allegations and also slapped a defamation case against Gen Singh.