The Centre has dispatched 20 teams of the NDRF and pressed into service Indian Air Force helicopters to help flood-hit people in Bihar, officials said on Monday.
The incident took place around 2.20 pm when part of a staircase of the residential building, located near Khar Gymkhana, came crashing down, he said.
Deputy Inspector General of Police Md Ehsan Raza said 19 bodies were recovered so far and many more could be trapped inside the boat.
Heavy rains lashed the catchment areas of the Krishna and Varana rivers on Monday morning following which their water levels rose.
The current flood situation in different parts of the country and the preparedness of central ministries and agencies to deal with it was reviewed at a high-level meeting chaired by Union Minister of State for Home Nityanand Rai.
More than 60 villages in the two districts remain marooned due to heavy discharge of floodwaters from upstream Bhadrachalam in the neighbouring Telangana state, where the water levels had reached 45 feet by afternoon.
The train, with around 700 passengers, had left Mumbai for Kolhapur on Friday night, but could not travel beyond Chamtoli, where it reached early Saturday.
Twenty-eight people were injured after the four-storey building, which housed a restaurant, collapsed on the Nahan-Kumarhatti Road on Sunday evening following heavy rains, they said.