Karti Chidambaram arrived at the CBI headquarters in New Delhi around 11.30 am and was questioned extensively till 6.30 pm.
Three suspected associates of Karti Chidambaram - Bhaskar Raman, Ravi Vishwanathan and Mohanan Rakesh - were also questioned in connection with the case, the sources said.
They said all the four persons were questioned separately and information given by them is being scrutinised.
It is only after the analysis of their responses that a call will be taken whether further interrogation is required or not in the case, they said.
The sources said they have been asked to produce some documents which they have agreed to provide.
The sources said a firm "indirectly controlled" by Karti Chidambaram received money from INX Media, run by the Mukerjeas, who are currently in jail, charged with the murder of Indrani's daughter Sheena Bora.
The CBI had also questioned Karti Chidambaram on August 23.
P Chidambaram had earlier issued a strong statement in response to the CBI's FIR against Karti Chidambaram, 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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