Repair work was going on urgent basis at the rail bridge, lifeline of the North Bengal, a Northeast Frontier Railway official said.
Assam-bound locals and some long distance trains were being diverted to alternate routes, the official said.
There was no report of cancellation of trains as of now but they were running late by hours, the official said.
The stretch of track connect Sevoke, North Bengal with the Hills.
Meanwhile, torrential rains flooded low-lying areas of Mal sub-division and inundated a large part of Jalpaiguri town as rivers Teesta and Karala were in spate, a district official said.
The rains have affected 4,000 people.