NEW DELHI - A portion of a four-storey building in India's financial capital collapsed in heavy monsoon rains, killing at least five people, the authorities said on Tuesday.

Rescuers used sensors and life detectors to find another five people still trapped in the debris of the building in the Sion area of Mumbai, said Mr Vijayendra Dahiya, an official at the National Disaster Management Authority.

Another six people were injured when the part of the structure caved in Monday night. Police cordoned off the building fearing more of it could collapse.

Building collapses are common in India as builders try to cut corners by using substandard materials, and as multi-storied structures are built with inadequate supervision.

Mr Dahiya said the cause of the collapse was not immediately known.

In April, 74 people were killed when an eight-story building being constructed illegally in the Mumbai suburb of Thane caved in. It was the worst building collapse in the country in decades.

The massive demand for housing around India's cities and pervasive corruption often result in builders adding unauthorised floors or putting up illegal buildings.