More than 200 sleuths of the I-T department swooped down on the premises of Mittal and his relatives as the department has found a number of contracts to the tune of more than Rs 200 crore being bagged by them, sources said.
Mittal is considered to be close associate of former BJP President Rajnath Singh and late party leader Pramod Mahajan.
The department also carried out searches at the premises of three-four big contractors at more than 20 locations in the National Capital Region including some foreign companies who have their consortiums in India, they said.
Sources in the department said the I-T probe will specifically look into the contracts awarded by the Games Organising Committee and the role of its officials and contractors including charges of bribing.
The I-T department officials will be seizing documents related to all the tenders and contracts being granted to various consortiums for the Games to detect possible evasion of taxes through over-invoicing and under-reporting of accounts.

The department is already in possession of documents related to award of contracts which were sourced from the OC and various other government agencies.
The I-T department is also scrutinising financial documents relating to the broadcast rights for the Games following charges of tax evasion.
The department has conducted survey operations on the Indian arm of a London-based broadcast company and has found alleged discrepancies in the tax statements of the company.
The department is investigating if the discrepancies to the tune of crores of rupees are related to the earnings of the company from its deal with the OC and possible tax evasion, they said.
Source: PTI