Karti Chidambaram arrived at the CBI headquarters in New Delhi at 11:30 am.
Three suspects linked to him -- Bhaskar Raman, Ravi Vishwanathan and Mohanan Rakesh -- are also being questioned today in connection with the case, the sources said.
The CBI is examining him in connection with a Foreign Investment Promotion Board (FIPB) clearance given to media group INX Media for receiving funds from Mauritius when his father P Chidambaram was the finance minister.
The sources said a firm "indirectly controlled" by Karti Chidambaram allegedly received money from INX Media, run by the Mukerjeas, who are currently in jail for murdering Indrani's daughter.
The CBI had also questioned Karti Chidambaram on August 23.
P Chidambaram had earlier issued a strong statement in response to CBI's police complaint against his son, saying the government was using the CBI and other agencies to target his son.
The FIPB approval was granted in "hundreds of cases", the senior Congress leader had said.