A powerful blast occurred at Hindusthan Unilever office in central Kolkata's Shakespeare Sarani on Wednesday morning injuring about 25 people.

Police sources have refused to confirm whether the blast was an act of terrorism. A bomb disposal squad has been called in and two fire brigade engines have also reached the spot.

Speaking to rediff.com, police sources hinted that a faulty transformer could have triggered the blast, but no confirmation was available immediately.