A woman was injured on Tuesday when a bomb kept in a container underneath a pile of garbage exploded in the city's Ekbalpur area, police said.
The incident occurred around 3 pm, they said.
On receiving information, police reached the spot and seized three more bomb kept in containers from underneath the garbage pile, they said.
The woman was rushed to a nearby hospital where she received primary medical care and then discharged, police said.
"We are looking into the matter and trying to find out who hid those container bombs there. We are checking the CCTV footage and also speaking to the locals," a senior officer of Kolkata Police said.