An old four-storey building collapsed in India's financial capital of Mumbai on Tuesday, trapping more than two dozen people in the rubble, with at least four confirmed dead, a fire department official said.

It was the second such collapse around Mumbai in less than ten days. Torrential rains that lash the city during the monsoon often destabilize older or badly constructed structures and this has led to multiple collapses over the years.

"We don't know exactly how many, but with the input provided by neighbours, we estimate more than 30 could be trapped," said the official, adding that rescue operations were hampered by narrow lanes in the area.

A Reuters witness at the site said residents were helping with rescue efforts and that those injured were being carried by hand to nearby ambulances that were unable to access the site.

Devendra Fadnavis, chief minister of Maharashtra state in western India, said that based on initial information around 15 families were living in the building which he said dated back 100 years.

He said the focus was on rescue efforts, but that the government would open an investigation. Police said at least seven injured people had been taken to hospital.