KOLKATA, INDIA --Rescuers in Kolkata dug through large chunks of debris from an overpass that collapsed while under construction Thursday, killing at least 21 people and injuring scores of others in trapped cars, trucks and other vehicles, officials said.
Army troops joined efforts to rescue those trapped inside vehicles that lay under massive concrete blocks and metal debris. Huge cranes and other rescue vehicles reached the site to clear the rubble.
The Press Trust of India news agency, quoting police sources, put the death toll at eight. More than 40 injured were admitted to two hospitals in Kolkata, the capital of West Bengal state, hospital officials said.
"The area was very, very crowded. Motorized rickshaws, taxis ... there was a lot of traffic," one witness told the New Delhi Television news channel, or NDTV.
Another added: "We heard a loud rumble and then saw a lot of dust in the sky."
PHOTOS: Dozens trapped in deadly India overpass collapse
Television images showed the bloody legs of some of the trapped people jutting out of the collapsed girders and concrete slabs
In addition to army troops, personnel of the National Disaster Response Force also worked on the scene in Bara Bazaar, a busy residential and shopping area in central Kolkata.
O.P. Singh, the NDRF chief, said the operation was a "very, very challenging task."
Building collapses are common in India, where builders use poor enforcement of regulations and use substandard materials.
We're following this story on Eyewitness News. Watch for updates on air, online and on our mobile news app.
Keep checking back on this page to get real-time updates as this story unfolds. To get alerts for breaking news, download the abc13 news app for iPhone or Android. You can also get breaking news alerts sent to you by email.
(Copyright 2016 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)