Kolkata, May 19 : After avoiding seven summons from the Central Bureau of Investigation (CBI) for interrogation in the cattle and coal smuggling cases in West Bengal, Trinamool Congress leader Anubrata Mandal on Thursday turned up at the CBI's Nizam Palace hospital here. His voluntary appearance at the CBI office happens 12 hours after the former state education minister and the Trinamool Congress secretary general, Partha Chatterjee was grilled for four hours at the same place on Wednesday evening. Chatterjee was being probed in the West Bengal School Service Commission (WBSSC) recruitment irregularities scam. Incidentally, Mandal's voluntary appearance also happens two days ahead of the May 21 deadline for him. In his last communique to the CBI, Mandal, the Trinamool Congress' Birbhum district president, had informed that till May 21 he would not be able to meet the central agency sleuths as a medical report of the state-run SSKM Medical College & Hospital had advised him complete bed rest till that period. However, quite to the surprise of the CBI sleuths, they received a communique from Mandal late Wednesday evening about just an hour after Partha Chatterjee left the office. In that communique, Mandal said that he would be reaching the CBI office on Thursday morning by 10 a.m. Accordingly on Thursday morning, Mandal started from his residence at Chinar Park in the northern outskirts of Kolkata at around 9.10 a.m. and finally his vehicle reached the CBI's Nizam Palace Office in central Kolkata. He refused to answer the queries of the mediapersons and went straight into the elevator. A team of CBI sleuths led by the agency's joint director, Prakash Srivastav was waiting there with a seven-page list of questions. Legal brains believe that in all probability Mandal has exhausted all his legal options to avoid the CBI questioning, and hence he decided to join the probe. The political observers feel that the event of Partha Chatterjee, currently the state commerce and industries minister, being compelled to face the CBI grilling might have made Mandal feel that he should voluntarily appear at the CBI office without further delay. /IANS