The bridge which connected the area near the Times of India building with the iconic CST station was commonly known as 'Kasab bridge' as the 26/11 Mumbai attack terrorist passed through it during the terror strike.
All the injured have been rushed to nearby hospitals, a disaster management cell official said.
An eywitness said when the bridge collapsed, there was a red light at the nearby signal, and that is why the death toll was not more.
Another eyewitness said the overbridge was being used despite repairs being carried out this morning.
The incident took place around 7.30 pm when a major portion of the bridge caved in, the official said.
Some motorists who were passing beneath the bridge when it came down, were among those injured, he added.
"Fire brigade personnel reached the spot immediately and rescue work is in full swing. We have appealed the motorists to avoid the D N road to JJ flyover section," he said.
"Foot over bridge connecting CST platform 1 north end with B T Lane near Times of India building has collapsed. Injured persons are being shifted to hospitals. Traffic affected. Commuters to use alternate routes. Senior officers are on spot, Mumbai police tweeted.
The 26/11 attacker Ajmal Kasab had used the bridge during the 2008 Mumbai terror attack.