It said the searches and survey operation was carried out at 20 premises linked to the group, which also has a dealership of petrol pumps, between March 17-20.
Over Rs 4 crore worth of cash and jewellery has been seized during the operation, it said.
"The group was indulging in manufacture and sale outside the books and was using an extensive network of shell companies to plough back unaccounted income.
"Preliminary findings include the sale of unaccounted production of Rs 185 crore," the Central Board of Direct Taxes (CBDT) said in a statement.
It added that accounts of actual production details, which are "not recorded" in regular books, have been recovered.
"The products of this group (like sponge iron, mild steel ingots and rods and TMT bars) are used in building construction and other infrastructure projects, and unaccounted production is sold in cash in eastern India.
"The cash generated (about Rs 100 crore) is being ploughed back into the group in the form of share capital and unsecured loans from Kolkata-based shell companies," it alleged.
The money was also invested by the promoters of the group in the purchase of properties and expensive personal items.
"The group has also obtained unsecured loans of about Rs 25 crore from Kolkata-based shell companies, clearly indicating the ploughing back of its own unaccounted income.
"It has obtained bogus commodity profit entries amounting to Rs 30 crore," the statement said.
An entry provider and a freight forwarder were also searched and these persons were arranging entries through shell companies, it claimed.
"Documents indicating such unaccounted entries have been found during search, establishing the nature of unaccounted transactions and entries taken by the group," the CBDT, the administrative authority for the tax department, said.
The search has revealed, it said, that the group was actively engaged in the generation of unaccounted income in cash and introducing the same as equity and loans and making investments in real estate.
Unaccounted cash of Rs 3.07 crore and bullion and jewellery worth Rs 1.28 crore was seized during the search, it said. PTI NES KJ