Karuna Sagar, a senior officer with the Tamil Nadu state police force, said the confirmed death toll from the disaster on the outskirts of Chennai now stood at 42. At least five people were still unaccounted for.
"The death toll was 31 but it has risen overnight. It now stands at 42," Sagar told AFP.
"Rescue efforts will continue while there is still hope of finding even a single survivor."
Emergency workers had pulled out four survivors on Tuesday, raising the hopes of rescuers and the families of those still missing.
A senior officer of the National Disaster Response Force (NDRF) said every life saved spurred on his team of 400 workers.
"Even a single life is precious for us," Sandeep Roy Rathore, an NDRF inspector general, told the NDTV network.
"Even if... (we) have to go round the clock for the next three to four days, we will do that. We will find anybody who is alive."
Rescuers have been using drills to go down vertical shafts with the help of mechanical diggers and heavy-cutting equipment like saws and chipping hammers.
Most of the victims were construction workers, who were reportedly in the building to collect their wages.
Six people have been arrested so far for negligence, including the chief builder and the architect.
The collapse came only hours after a dilapidated apartment block crumbled in the capital New Delhi, killing 10 people including five children.
A massive influx of people to cities in search of jobs and a shortage of low-cost housing has helped fuel the construction of illegal buildings across the country, often made using substandard material.
Millions also live in dilapidated old buildings, many of which cave in during rains.
In September last year more than 50 people were crushed to death when a five-storey building collapsed in India's financial hub Mumbai.
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Amma brand collapses because it is all based on populist measures. the day tamilnadu stops being populist and stop giving TV , fridge , mixers, grinders and other stupid stuff for vote, they can build stronger economy and robust infrastructure till then this is bound to happen.