The toll in the Kolkata warehouse collapse incident rose to 16 on Saturday with the death of an injured person in a hospital, while rescue teams from multiple agencies sifted through the debris on the fourth day since the incident to ensure no one is still trapped, officials said.

Cameras have been placed beneath the rubble to check for trapped persons, while mobile phone tower data is being used to trace the location of individuals whose phones remain active under the debris.

"Our first priority is to complete the search and rescue operation. Teams are carefully checking every part of the collapsed structure. Massive debris clearance will start only after we are fully satisfied that no one is trapped inside," an official said.

Large-scale debris removal will begin only after rescue personnel are certain that there are no more survivors or bodies under the rubble, he said.

A senior state government official said, "A person, Khalek Sardar of Basanti, undergoing treatment at the hospital, died. With this, the toll in the incident rose to 16, with 17 others undergoing treatment." He said the rescue operation was being carried out with utmost caution to avoid any risk to rescuers and to ensure that no victim was missed.

The Indian Railways joined the rescue operation on Friday after the NDRF sought its assistance in cutting and removing twisted steel structures to facilitate the search for those feared trapped under the debris.

The warehouse, which was being constructed, collapsed on Wednesday afternoon. The body of the principal contractor, who was among the five people named in the FIR registered in the case, was recovered from the site.

Police have formed a Special Investigation Team to probe how the structure collapsed.

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