The bus was heading for Durgapur from Jhargram when it got washed away as it was crossing the Amritpal bridge near Phulkusuma village at about 1:30 pm, Bankura Superintendent of Police Mukesh Kumar said.
Chief Minister Mamata Banerjee told reporters at the state secretariat in Kolkata, "Three or four passengers of the bus are missing.
"There is no passenger inside the bus at present, she said.
Kumar said that 43 passengers were rescued from the bus with the help of local people.
Earlier,police had said that the bus was carrying 70 passengers.
The driver lost control and the bus skidded as it was crossing the bridge when it was raining hard, she said.
A disaster management team was at the accident spot which is between Khatra and Raipur, she said.
Child development minister Shyamapada Mukherjee and the SP and have been sent to the spot,Banerjee said.
