The CBI sources said that two other executives of Vectra and two businessman, whose premises were searched, were also questioned.
The agency has registered a case with regard to alleged offer and carried out searches at seven locations in the national capital, Noida and Mumbai.
Sources claimed a business man alleged to be having close links with Rishi was also searched in which huge cash was recovered.
He was also called for questioning at the CBI headquarters today along with another businessman, they said.
The agency is trying to look into links of Rishi with Tejinder Singh, the sources said.
The CBI has named Singh as prime accused in the case registered under section 12 of the Prevention of Corruption Act.
Singh did not respond to SMS sent seeking his reaction.