Rescuers search for workers believed buried in the rubble of a building that collapsed during monsoon rains in the outskirts of Chennai (AP)

Rescuers in India have pulled seven more survivors from under the ruins of a collapsed building, three days after it fell.

At least 29 people have died after the 11-story building in a suburb of Chennai collapsed.

Already, 26 people have been rescued alive from under the enormous heap of broken slabs, twisted iron girders and concrete dust where the apartment building was being constructed, the National Disaster Response Force said.

Hundreds of rescue workers, wearing hard hats and breathing masks, are likely to continue searching for at least another day. They expect to find more bodies, with rescuers saying foul smells at the site have become overpowering

"As a rescuer, we don't lose hope," said disaster response official Sandeep Rai Rathore. "It will take time ... Removing the debris layer by layer is very difficult."

Three diggers were working to clear the area but rescuers are working carefully and slowly to avoid disturbing the debris, which could still shift and settle further potentially crushing anyone still trapped.

Instead, they are listening for faint cries and thuds coming from the debris pile to guide their search, but by this evening no sounds were being heard, Mr Rathore said.

When the building collapsed on Saturday night, nearly 90 contract workers - most from neighbouring Andhra Pradesh state - were in the basement collecting wages.

Earlier today, officials said 55 people had been rescued. But information officer Thangaraju, who is with the Disaster Response Force, clarified that number includes the dead.

Police have arrested six construction company officials for alleged criminal negligence and violation of building codes.