Two sweepers of the hospital suffered injuries in the blast. According to sources, the explosive carbide material was placed in a plastic container and went off when the hospital employees shook it.
The bomb squad has been rushed to the spot and hospital services have been briefly stalled.
Latest reports suggest that a petrol bomb might have been used in the bomb blast in Kolkata. The Medical College Principal Shiddhartha Chakraborty said normal hospital services were not affected.