A flyover under construction in the bustling city of Kolkata collapsed on to moving traffic below, killing at least 14 people with as many as 150 people feared trapped, police said.
Residents were using their bare hands to try to rescue people pinned under a 100-metre length of metal and cement that snapped off at one end and came crashing down in a teeming commercial district near Girish Park.
The 2-km flyover has been under construction since 2009 and has missed several deadlines for completion.
Construction projects in India have long been plagued by lax safety standards and dubious ties between politicians and business.
The disaster could play a role in the West Bengal state election, one of five being held from next month that will give a verdict on Prime Minister Narendra Modi's nearly two years in power.