A senior officer from the National Disaster Response Force which is leading the search, S.P. Selvan says the operation is a big challenge.
"There is no clarity on the number of people trapped," he reportedly told media in Chennai.
Tamil Nadu Chief Minister Jayalalithaa Jayaram says the collapse appears to have been the result of poor construction.
"From investigations conducted by our senior officers, it appears that the building plans that were approved were not strictly adhered to by the builders," she said.
"There was nothing wrong with the plans that were submitted for approval but the builders...did not adhere to the plans that have been approved.
"It is too early to say exactly what went wrong but there appears to have been serious structural defects...tests have to be conducted to see whether the soil is suitable, whether the soil is capable of bearing such a huge weight."
Jayalalithaa Jayaram, has announced compensation of 200,000 rupees ($USD3,000) for the families of the dead and 50,000 rupees for those injured.