Kalmadi reached the CBI office at about 10 AM. His questioning began about half an hour later, official sources said.
The questioning is about alleged irregularities in the Queen Baton`s Relay held in London last year besides certain contracts awarded to various firms totalling several hundred crores, the sources said.
The agency had raided his Pune and Delhi premises on December 24 during which several documents including digital were seized, they said.
The sleuths have grilled Kalmadi`s three key aides in connection with the scam. The sources said Manoj Bhori, political advisor to OC head and P K Srivastava and A K Sinha, both assistants to Kalmadi, were also called for interrogation.
Besides Kalmadi, the CBI had also conducted raids at the residence of OC Secretary General Lalit Bhanot, R K Sacheti, who is Joint Director General of the OC, and Sangeeta Welingkar, member of the Games Image and Look Group.
The agency has so far filed three FIRs in connection with the alleged financial irregularities.
While one case is related to a Rs 107-crore deal struck with a Swiss score keeping firm, the CBI had registered two other FIRs in connection with the contract given to AM Films for the Baton Relay ceremonies by the OC in London.