Sources say that midway through the raids, the Oswal managers announced that much of what the sleuths might categorise as their concealed income had already been disclosed by them under the Government's 1998 Voluntary Disclosure of Income Scheme (VDIS).

There are indications that the Oswal group may have declared approximately Rs 30 crore under VDIS, which will ultimately reduce the liability fixed on them once the investigations are completed.

In all, the I-T department conducted searches and surveys in 55 premises owned by the two branches of Oswal group of industries. The premises were located in New Delhi, Mumbai, Ludhiana, Jalandhar and Bhopal. The simultaneous raids lasted over 24 hours.

At the end of the marathonexercise, the raiding parties returned with thousands of sheets of documents, copies of banking transactions and laptop computers. The tax sleuths are investigating whether the documents reveal diversion of funds into shell companies floated by the Oswals of crores of rupees.

Following the raids, 10-year block assessments of the group are to be opened by the I-T authorities, commencing from 1989.

I-T officers say they had put the Oswal companies under surveillance for the past three months and had prior information about the existence of about 10 such shell companies. But the raids have apparently shown the existence of double the number of shell companies, which the Oswals were allegedly floating and closing down in a typical case of money laundering.

Sources say the I-T department may have a voluminous and unwieldy case in their hands. Yesterday's raids have led the authorities to details of around 100 bank accounts operated by the Oswals in different parts of the country which clearly indicatetransactions with the shell companies.

Oswal group officials will be questioned about the ownership of the shell companies and the computer codes for the laptops seized. ``If the company officials do not give us the codes, we will crack the codes ourself. This has become a major case for us,'' a top I-T official admitted.