An under-construction flyover collapsed in Varanasi on Tuesday, killing 12 people while over 50 persons are feared trapped under the debris.
Many cars have been buried under the heap of rubble, district officials said, adding that the death toll could go up.
Rescue operation has been initiated to clear the debris of the flyover, which was being constructed by the Uttar Pradesh State Bridge Corporation.
Modi tweeted: "Extremely saddened by the loss of lives due to the collapse of an under-construction flyover in Varanasi. I pray that the injured recover soon. Spoke to officials and asked them to ensure all possible support to those affected."
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