Banerjee, who returned this morning from her eight-day visit to the Vatican and Germany, refused to take questions on the release of her former cabinet colleague who was yesterday granted bail by the Alipore court.
However, the chief minister's co-traveller Kolkata Mayor Sovan Chatterjee said Mitra's arrest was "politically motivated".
Mitra, then Sports and Transport Minister, was arrested by CBI on December 12, 2014.