Local residents cheered as emergency workers from the National Disaster Response Force (NDRF) pulled 20 survivors - including two boys aged four and seven - from the rubble of the building in Bhiwandi, near Mumbai.
An NDRF spokesman told reporters that emergency workers had retrieved 15 bodies from the rubble.
NDRF director general Satya Narayan Pradhan tweeted that specialist teams and sniffer dogs were trying to rescue another "20-25 feared trapped".
An official at the Thane city authority, which oversees Bhiwandi, told AFP that more than 40 emergency workers were helping search for survivors.
Images broadcast on the NDRF's official Twitter feed showed emergency workers combing through concrete and brick rubble with electrical wires hanging over their heads.
The cause of the pre-dawn accident was not immediately clear, but building collapses are common during India's June-September monsoon season, with old and rickety structures buckling after days of non-stop rain.
