An under-construction flyover in a congested market area in the Indian city of Kolkata collapsed on Thursday killing at least 21 and injuring more than 60 people. A rescue mission is under way to help people still stuck under the structure.

The death count is likely to increase as a number of people inside vehicles are still trapped under the collapsed 100-metre portion of the 2.2 km flyover.

The Vivekananda flyover was being constructed over a crowded marketplace, BurraBazar, to connect the central part of the city with the north. The incident took place on Thursday morning when a portion of the bridge suddenly came crashing down on the pedestrians and the traffic below it.The disaster has been called as an “act of God” by K.P. Rao, a representative of the construction company IVRCL, which was contracted to build the bridge. An FIR has been launched against the local officials of the company.

The disaster has been called as an “act of God” by K.P. Rao, a representative of the construction company IVRCL, which was contracted to build the bridge. An FIR has been launched against the local officials of the company.

The National Disaster Response Force responded to the carnage immediately with five of its teams.  Specialist rescue teams, with concrete and metal cutters, sniffer dogs, sensors to detect life and drilling machines arrived at the scene around 2 pm.

“We have deployed five columns of personnel along with a team of engineers. A medical team from the Command Hospital is also at the spot,” said S. S. Birdi, a spokesperson for the Ministry of Defence Wing Commander.

However, many of those involved in the rescued efforts appeared to be local people, the Hindu reported.

The BBC reported that a CCTV footage of the moment the bridge came crumbling down on the passers-by and the vehicles underneath is being circulated over the social media.

“There was a loud sound which scared us. The concrete had been laid last night at this part of the bridge,” Ramesh Kejriwal, an eyewitness told Reuters.

West Bengal Chief Minister Mamata Banerjee said that the state government will take “stringent actions” against the construction company.