Emergency workers in Kolkata continued to search for survivors underneath a collapsed flyover in a congested area of the eastern city, as the construction firm building the flyover was being investigated.

At least 23 people were killed and more than a dozen were still trapped under the rubble of the under-construction overpass that collapsed in the busy Burrabazar area on Thursday.

Rescuers were using sniffer dogs and special cameras to find trapped people and used saws, small cranes, and their bare hands to dig through the wreckage in search of victims.

Smashed yellow taxis, destroyed rickshaws and the bloody legs of trapped people jutted from the collapsed girders and concrete slabs.

"The condition is pathetic. At this moment no one has any clue how many people are trapped," said Raichand Mohta, a police officer at the scene.

The overpass spanned nearly the width of the street and was designed to ease traffic through the crowded Bara Bazaar neighborhood [AP]

Al Jazeera's Divya Gopalan, reporting from Kolkata, said the accident occurred in a "very busy area and the rescue operation is too slow.

"Heavy machinery, cranes, diggers are trying to break through the large slab of the flyover that has fallen on to the ground to rescue people trapped under the rubble.

"However, what is making this rescue operation more difficult is that this area is very congested and densely populated. And the flyover is built in between residential buildings.

'Body parts strewn all over'

Local TV footage showed a street scene with two auto rickshaws and a crowd of people suddenly obliterated by a mass of falling concrete that narrowly missed cars crawling in the traffic jam.

"Before the ambulances arrived, we were here at the location trying to rescue the people out of the rubble. There were body parts strewn all over the place," a witness told Al Jazeera. 


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Police said 39 of more than 70 people taken to hospital were still being treated on Friday morning.

Getting survivors to hospital was also complicated by the lack of access for ambulances to the flyover. Safety standards were lax, witnesses said.

"Every night, hundreds of labourers would build the flyover and they would cook and sleep near the site by day," said Ravindra Kumar Gupta, a grocer, who pulled out six bodies, together with his friends.

Investigation launched

Police launched an investigation into the construction firm building the flyover, the local government said, and had reportedly sealed its offices.  

India n company IVRCL was building the 2km Vivekananda Road flyover, according to its website, and its director of operations, AGK Murthy, said the company was unsure of the cause of the disaster.

"We did not use any inferior-quality material and we will cooperate with the investigators," Murthy told reporters in Hyderabad, where the firm is based. "We are in a state of shock."

The Associated Press reported that police officials detained five construction company officials on Friday.

Construction collapses are common in India, where regulations aren't strictly enforced and builders often use substandard materials.

Rescue workers cut through parts of the overpass to recover vehicles [AP]

Source: Al Jazeera and agencies