IBTimes UK

Hundreds of rescue personnel worked through the night searching for people trapped under the debris of a collapsed city overpass in eastern Indian city of Kolkata.

Officials have confirmed at least 23 people died when the under-construction flyover in the city's Girish Park area collapsed with a loud thud on Thursday afternoon.

The controversial flyover, 2 kilometers long, had passed several deadlines since the construction began in 2009.

Meanwhile a senior official of the company building the bridge said the collapse was "an act of god," adding that the company, Hyderabad-based IVRCL, has good safety record.

Lack of safety protocols and the use of substandard materials have often plagued mega public construction projects in India.

People and vehicles on a busy road in the city came under the steel and concrete rubble of the flyover came crashing down in a densely populated neighborhood in the city.

Unconfirmed media reports said at least 150 people were trapped under the rubble. More than one bus full of passengers was trapped under the flyover rescue forces said.

"We heard a noise and got scared. Yesterday (the bridge) was welded. The bridge collapsed. I think at least 150 people are under the debris," an eye-witness told ANI.

Construction company IVRCL denied there was any compromise on construction quality. "It's nothing but God's act," senior official K. Panduranga Rao said, according to the Press Trust of India.

Problems with the scaffolding and negligence probably caused the collapse, the Telegraph newspaper published from the city reported, citing engineers not associated with the project.

Toll could rise

It said residents witnessed several bolts coming off the flyover and falling on to vehicles moving underneath, hardly a few hours before the collapse.

"Some of the workers were brought down around this time," a fruit vendor told the daily.

Maj. Gen. Anurag Gupta of India's National Disaster Management Authority, said the death toll may climb and that it's not clear how long the rescue effort will last.

"We cannot predict how many people are still under wreckage. We can't tell since it's a bridge and not a building," he told CNN.