The incident occurred near Ganesh Talkies (Girish Park), Thursday afternoon, with reports of a large number of people were also injured.
“The condition is pathetic. At this moment no one has any clue how many people are trapped,” said Raichand Mohta, a police officer at the scene.
According to medical sources, around thirty people have been rushed to hospitals and many more are yet to be rescued.
Eyewitness said they heard a loud explosion and then a crashing sound. “A cloud of smoke emerged from the collapse,” they said.
The 2km-long (1.2 mile) flyover has been under construction since 2009 and missed several deadlines for completion, Reuters news agency says.