At least 15 were killed and many trapped when an under-construction bridge collapsed in the eastern Indian city of Kolkata. Photo: Getty Images

USING saws, small cranes and bare hands, rescuers searched for survivors under the crumbled concrete and twisted steel from an overpass that collapsed onto a crowded Kolkata neighbourhood, killing at least 23 people and injuring more than 80.

With more than half the debris cleared by Friday morning, 67 people have been pulled out alive, Kolkata police Sgt. P.

Chakraborty said. But more people were still feared trapped. It was not clear how many are missing.

Smashed yellow taxis, a crushed truck, destroyed rickshaws and the bloody legs of trapped people jutted from the fallen girders and concrete. Building and other construction collapses are common in India, where regulations are poorly enforced and companies often use substandard materials.

The partially constructed overpass spanned nearly the width of the street and was designed to ease traffic through the densely crowded Bara Bazaar neighborhood in the capital of the east Indian state of West Bengal. The steel girders had already been fixed, and on Thursday the concrete was poured into the framework.

Within hours, as the concrete was drying, about 100 metres of the overpass fell, while other sections remained standing.

“I heard an explosion, a solid one,” said resident Rabindra Kumar Gupta, who had been home eating lunch when the overpass crashed down around 12.30pm yesterday. “My apartment shook. The whole building shook. When I looked outside, there was a lot of smoke.” Another resident, Yogesh Sharma, described a “huge crashing sound” when the overpass came down as he was been sitting at a roadside tea stand with friends.

“I left my cup of tea and ran,” said Sharma. “I was crying at the spot.” Crowds waited anxiously near the rescue area to see if neighbours and friends had survived. The intersection had been a place where street vendors and service workers regularly plied their trades. “There used to be a tailor who sat here on this corner. We wonder about him. A cigarettes and tobacco vendor - we knew everyone who used to stay around this crossing,” resident Pankaj Jhunjhunwala said. “Until this rubbish is removed, we can’t say for sure where they are or how this happened.” Police said 39 of the more than 80 people taken to hospitals were still being treated Friday morning. At least 23 people were killed.

With army troops and personnel from the National Disaster Response Force joining the effort, police said they expected the rescue and cleanup to be completed on Friday.

Workers in yellow hard-hats operated huge cranes, bulldozers and other equipment through the night to clear the rubble and pry apart the concrete slabs. They also used cutting torches to break up metal beams.

The operation was a “very, very challenging task,” said O.P. Singh, chief of the disaster response force. Rescuers also used dogs and special cameras to find people who were trapped, he said. “The area was very, very crowded. Motorized rickshaws, taxis ... there was a lot of traffic,” one witness told NDTV television. Prime Minister Narendra Modi, who was in Washington at the time of the collapse, called Chief Minister Mamata Banerjee, the top elected official of West Bengal state, to express grief at the tragedy and pledge federal support.

He said he was “shocked and saddened,” according to a message on his Twitter account. “My thoughts are with the families of those who lost their lives in Kolkata. May the injured recover at the earliest.” Banerjee, whose has been campaigning for re-election this month, told reporters that a private builder had missed several deadlines for completing the construction.

The contract for the overpass was signed in 2007 and it was expected to be completed in two years. Banerjee accused the previous Communist government in West Bengal of not adhering to building regulations.

More than 100 feared trapped after fatal overpass collapse in Kolkata: https://t.co/XUKkuRBRtihttps://t.co/6yDMU0TGYM — Reuters Top News (@Reuters) March 31, 2016

“We completed nearly 70 percent of the construction work without any mishap,” said K.P Rao, a top official of IVRCL Infrastructure company, which was building the overpass. “We have to go into the details to find out whether the collapse was due to any technical or quality issue.” Police have sealed the Kolkata office of the Hyderabad-based construction firm involved in building the overpass. It is also investigating the firm’s officials for alleged culpable homicide, punishable with life imprisonment, and criminal breach of trust, which carries a prison sentence of up to seven years.