He also said that "sizeable volume of cash and documents" have been seized at the searched premises.

"The volume and value of cash and documents seized would be known only after they are totalled after completing the entire operation," he told IANS preferring anonymity.

"In some places the search operations have ended and in many places the it is still going on," he added.

The searches were conducted in connection with unexplained routing of cash post-demonetisation through shell companies allegedly connected to Sasikala and Dinakaran.

The IT department will look at the routing of funds within India whereas other agencies will look into the routing of money outside India, the official said.

According to him, the nature of this search operation "is different" and it is not just searching the premises and seizing unaccounted cash.

"We have information about shell companies and the search is in connection with their operations," he said.

Whether the bank accounts of the searched persons, companies would be "frozen to detect suspect transactions and other actions", would be taken only after collating the data from the seized papers.

On Thursday, a team of around 1,800 IT officials knocked at the doors of 187 premises-residences, offices and farm houses -- to carry out one of their biggest searches on the members, business establishment and business associates of one single family, that is, Sasikala's.

The places raided included the residence of M. Natarajan, Sasikala's husband, in Thanjavur, Kodanad Tea Estate belonging to late Tamil Nadu Chief Minister J. Jayalalithaa, Jazz Cinemas, Midas Distilleries, Sharada Paper and Boards, Senthil Group of Companies, Nilgiri Furniture in Coimbatore, Jaya TV, Namadhu MGR and several other premises in Tamil Nadu, Puducherry, Hyderabad and Bengaluru.

The operation was kept secret, so much so that the raiding tax officials hired private cabs and had pasted wedding stickers on the windscreens of vehicles involved in the operation so as not to arouse suspicion.