TORRENTIAL rain in India has caused a five-storey apartment building to collapse in Mumbai, killing 16 people and possibly burying more than a dozen more under the debris, police said.

Rescuers, residents and police officers managed to pull 30 injured people from the rubble, but more than a dozen were missing and feared trapped.

The building was one of thousands in Mumbai that are more than 100 years old, with foundations that have been weakened by years of heavy monsoon rains.

Last month, another four-storey building toppled in the city’s suburb of Ghatkopar, killing 17.

Thursday’s tragedy occurred in a congested area of Mumbai’s southern Bhendi Bazaar area, following the city’s heaviest rainfall in 15 years.

Authorities were advising people living in an adjacent building to vacate after it developed cracks following yesterda's early morning collapse. It was not immediately clear how many people might be trapped in the toppled building.

“We are asking people to check if their family members are safe and accounted for,” officer Manoj Sharma said at the scene.

The building had housed nine families in apartments above a first-floor nursery school, but the collapse occurred before the toddlers had arrived for the day, police said.

Nearby resident Amina Sheikh tightly held her four-year-old grandson’s hand as they watched the rescue efforts from a safe distance.

“This is my grandson. He used to go to school in that building,” she said, tearfully pointing at the rubble.

She had been getting the youngster ready for school on Thursday morning when she heard a loud boom and saw the building had crashed down.

It was “an hour before his class began. That’s why my grandson’s life was saved”, she said.

Hours later, rescuers used earth-moving machines to lift concrete slabs and cement blocks as they searched for survivors.

Building collapses are common in India during the monsoon season, which is June to September.

High demand and lax regulations encourage some builders to use substandard materials or add unauthorised extra floors.

Property prices and rents are among the highest in India as Mumbai has expanded in the past five decades.

The city is slowly limping back to normality after it was paralysed by heavy downpours for two days. Train services and public transport were halted and airports shut on Tuesday as roads turned into rivers and floodwaters seeped into many low-lying buildings.

In many places, people had to abandon their vehicles and wade through waist-deep water to reach their homes.

Schools, colleges and offices that were shut on Wednesday opened on Thursday, but attendance was sparse.

Every year the city struggles to cope with the annual monsoon deluge, drawing criticism about its poor planning.

Since the start of the season, devastating floods across South Asia have killed at least 1000 people and affected close to 40 million across northern India, southern Nepal and northern Bangladesh.

The rains have led to wide-scale flooding in a broad arc stretching across the Himalayan foothills in the three countries, causing landslides, damaging roads and electric towers and washing away tens of thousands of homes and vast swathes of farmland.