Karti arrived at the CBI headquarters here at around 11.30 am.
Three suspected associates of Karti --Bhaskar Raman, Ravi Vishwanathan and Mohanan Rakesh -- are also being questioned on Monday in connection with the case, the sources said.
The agency 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 Union finance minister.
The sources said a firm 'indirectly controlled' by Karti received money from INX Media, run by the Mukerjeas, who are currently in jail, charged with the murder of Indrani's daughter.
The CBI had also questioned Karti on August 23. P Chidambaram had earlier issued a strong statement in response to CBI's FIR against Karti, 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.
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