Widespread heavy rainfall was recorded in the region during the two days which lead to land falling away beneath the tracks.

Trains were immediately suspended.

READ ALSO: NSW drenched by 'extraordinary' high rain

"The Blue Mountains Line is closed between Springwood and Mount Victoria due to a landslide at Leura on Sunday," a Sydney Trains spokesman said.

"Sydney Trains engineers have stabilised the track and are investigating the extent of the significant damage to the rail infrastructure.

"A full engineering assessment is expected to be completed in the next 24 hours."

The spokesman said a second landslide at Mount Victoria did not cause any significant infrastructure damage.

READ ALSO: When bushfire attraction means more than just an Instagram post

During the weekend, 259.4 millimetres of rain was recorded in Katoomba, including 193.4mm on Sunday alone.

This caused significant flooding across the area, including in the rail corridor.

READ ALSO: Snapshot of Australia's water supply

This closure follows significant damage to railway infrastructure in December and January when the Gospers Mountain bushfire swept through the Blue Mountains.

Limited buses are replacing trains between Springwood and Lithgow/Bathurst. Commuters are urged to allow plenty of extra travel time, listen to announcements and check indicator boards.

Customers travelling along the affected line can check the latest information and plan their journey through trip planning apps or online at Transport NSW.

Why not subscribe, the first 30 days of full website access is free.