Emergency work to repair a landslip beneath the railway between Kilmarnock and Dumfries will take a further four weeks.
The line has been shut near Holywood in Dumfries and Galloway since Monday in the wake of Storm Ciara.
Heavy rainfall has caused the nearby River Nith to erode an embankment beneath the railway.
Following detailed examination Network Rail said the line would need to stay shut until 16 March.
Engineers are currently working to repair the 1,700-tonne landslip beneath the 50m (160ft) stretch of track.
The line between Kilmarnock and Dumfries has been shut since Monday when an embankment collapsed.
Emergency works to repair a landslip beneath the railway between Kilmarnock and Dumfries will continue for a further four weeks.