Five days of torrential rain have led to severe flooding in the south Indian states of Karnataka and Tamil Nadu.
Traffic in Bangalore has been severely affected
Several hundred villages in Karnataka are threatened by the rising water levels of the Cauvery river.
Residents in India's technology hub, Bangalore, are also battling floods after three major lakes in the city breached their banks.
Many of the areas affected by the rainfall have been hit by severe drought in recent years.
The water level in many dams in Karnataka is overflowing. The Karnataka government has released excess water to the Mettur dam in the neighbouring state of Tamil Nadu, which has led to severe flooding in low-lying areas in Salem district.
In the Karnataka state capital, Bangalore, flooding was worsened by unauthorised developments along the three flooded lakes. Choked drains led to residential areas being inundated.
The BBC's Sunil Raman in Bangalore says an annual meeting of IT companies began on Wednesday amid growing concerns about the poor infrastructure.
Traffic has been severely affected. Thousands of office-goers were stranded on the city's waterlogged roads.
Schools in the city were closed and several apartment complexes flooded. Water entered some office-buildings, including one of the offices of India's third largest software exporter, Wipro.
Bangalore accounts for one-third of India's annual export revenue of $17.2bn in software and back-office outsourcing.
Karnataka Chief Minister Dharam Singh has held several rounds of meetings with senior officials. But they say little can be done until the rain stops.
Flooding in West Bengal state earlier this week claimed 19 lives and left more than 250,000 homeless, officials say.