The CBI early Thursday raided the residence of MK Stalin, son of DMK chief M Karunanidhi, triggering a political storm.
In New Delhi, finance minister P Chidambaram said he strongly disapproved of the CBI raid leading to reports that it had been called off.
However, a state intelligence official said that the search had "got over and was not called off".
The CBI was were tightlipped about the raid, which was carried out in connection with the import of a Hummer car used by Stalin's son Udyanidhi, the official said.
The raid began around 6am.
The search came two days after the DMK announced its decision to pull out of the Congress-led United Progressive Alliance (UPA) over the central government's stand on supporting a US-sponsored resolution censuring the Sri Lankan government on attrocities against Tamils during the civil war against the LTTE.
It is reliably learnt that the CBI registered the case in New Delhi and the raids were in connection with the import of cars and payment of customs duties.
The CBI also raided Stalin's friend Raja Shankar's house in this connection.
Reacting to the raids, Stalin told reporters that it was mere political vendetta and he would face all the legal issues.
Stalin is the third person in his family to be questioned by the CBI.
In 2011, the CBI questioned Stalin's mother Dayalu Ammal and sister Kanimozhi.
Kanimozhi and Dayalu Ammal were questioned in connection with the flow of over Rs. 200 crore from Swan Telecom promoter Shahid Balwa's DB Realty firm to Kalaignar TV, a regional Tamil channel in which Karunanidhi's family members allegedly have majority stake.
Later Kanimozhi was charged as co-conspirator in the 2G scam with former telecom minister A Raja, and lodged in Tihar jail. She is now out on bail.