Ten people died and 33 fishing boats went missing on Friday during monsoon storms in eastern India which flattened hundreds of homes and flooded the city of Kolkata, officials said.
Police said the deaths occurred in rain-related accidents across West Bengal, where 33 fishing trawlers and about 500 crew were also reported missing by a local fishing association.
Weather department official Gokul Chandra Debnath said the state capital Kolkata, where the downpour overwhelmed the inadequate and poorly maintained drainage system, recorded 10 centimetres (four inches) of rain on Friday.
"The city collapsed because we were not prepared for such a calamity at the beginning of the monsoon," Kolkata mayor Sovan Chatterjee said, adding an emergency response centre had been set up to help those stranded.
Senior police official Surojit Kar Purakayastha said at least 10 people were killed in the storms and heavy rains across the state.
Among those killed were four members of a family who died when a landslide flattened their home in mountainous Kurseong region and four others who were swept away after their boat sank in Kolkata's Hoogly river, he said.
Local fishermen's welfare association president Bijon Maity told AFP by telephone that 33 trawlers in the Bay of Bengal had gone missing during the afternoon.
"Each trawler has at least 16 fishermen," he said, meaning at least 528 men were unaccounted for.
During storms in West Bengal, many captains find themselves unable to return to port and take refuge with their boats and crews along the coast.
"We have urged the (state) chief minister Mamata Banerjee to take necessary steps to trace the missing trawlers," Maity said.
India has forecast a "normal" monsoon this year that could boost food production and ease high inflation.
The strength of the annual June-September downpour is vital to hundreds of millions of farmers and to economic growth in Asia's third-largest economy which gets 80 percent of its annual rainfall during the monsoon season.