Firefighters on Saturday morning recovered charred bodies of four unidentified persons from a building in North 24 Parganas, where a devastating fire broke out a day ago, reducing to ashes a vest manufacturing unit and other combustible item-filled godowns.

At least 30 fire fighters have been pressed into service since Friday to douse the blaze that raged on for almost 38 hours in the three-storey building in New Barrackpore's Bilkanada area.

A senior official of the fire department said the deceased are believed to be workers of the vest manufacturing unit, and the process to identify them was underway.

He also pointed out that fire tenders are currently putting out flames in pockets of the building.

"Drones were used to spot the four bodies, which would be sent for post-mortem after family members identify them," the official added.

Fire and emergency services minister Sujit Bose said a forensic team would be visiting the building to study and find out what led to the massive blaze.

"It's an unfortunate incident. We are sending the bodies for post-mortem to Sagore Dutta Hospital. A forensic team will visit the site and conduct tests to find out the possible cause of the fire," he said.