Kolkata, Nov 20 (IANS): Probing the multi-crore-rupee Saradha scam, the CBI Thursday raided three offices of the tainted group in the city.

Since morning, Central Bureau of Investigation (CBI) sleuths conducted searches at Saradha offices in different locations such as Salt Lake, Behala and Bishnupur in the city and seized documents.

The search operations come a day ahead of expected questioning by the CBI of West Bengal Transport Minister Madan Mitra and Trinamool Congress Rajya Sabha member Srinjoy Bose.

While Bose, who has been interrogated by the CBI once, claimed he was asked to appear as a witness, Mitra is undergoing treatment at a city hospital and said he will appear before the agency only if the doctors permit him.

Besides Mitra and Bose, former Trinamool MP Somen Mitra who has subsequently joined the Congress too has been summoned by the CBI.

Somen Mitra has denied getting any call from the CBI but insisted he would offer cooperation if the agency calls him for probe.