At least 23 people have been killed and more than 80 injured after a partially built overpass collapsed in the Indian city of Kolkata.
Emergency services, along with local residents, are frantically trying to rescue the dozens feared trapped under the wreckage in a busy commercial district.
The West Bengal city of Kolkata, one of India's busiest, has been forced into a chaotic standstill after what a local politician calls a "monumental tragedy."
Shoppers had been heading to the city's largest market at midday when a two-kilometre-long flyover, under construction since 2009, collapsed.
Eyewitnesses say the devastation initially sounded like a bomb blast.
(Translated) "There was a loud sound, which scared us. The concrete had been laid last night at this part of the bridge. I am lucky, as I was planning to go downstairs to have juice. When I was thinking about it, I saw that the bridge collapsed. Scores of people have been killed."
The fortunate few were able to escape, but this woman says many remain trapped under rubble.
"What my people who are there are saying is that there are buses and the minibuses and the taxis with the passengers trapped inside. So that is terrible news: a half-built bridge collapses in a congested area, and with many poor, homeless people the victims, buses and cabs with passengers are trapped."
Hundreds of rescue workers, led by soldiers, engineers and medics, have taken over the search and rescue efforts.
But local residents say progress has been slow, with others calling it an "uncoordinated response."
For the first few hours, volunteers were using their bare hands to move slabs of concrete, but this man says efforts became more sophisticated.
(Translated) "I saw a man waving at us for help from under the debris. I gathered some other residents, some army personnel, and, with some help from a crane, we could rescue the man. The man is being sent to a hospital now."
The director general of India's national disaster response team, O.P. Singh, says rescuers are using thermal cameras to try and find those missing.
And he says cranes have been brought in to remove the rubble.
(Translated)"Our biggest challenge is rescuing the huge number of people who are trapped under the debris, because there is a lot of concrete, so we are using cutters of all sorts to make holes in the debris so that we can make an entry. Only once we gain entry will the situation of the people trapped become clear."
Safety issues, including a lack of inspections and the use of inferior materials, have crippled construction projects across India for years.
While the cause of this latest disaster is still unknown, investigators have promised to determine exactly what happened.
