Network Rail is warning that a stretch of the Settle to Carlisle railway line could take up to 12 months to repair.
A landslip at Eden Brows, near Armathwaite, has destabilised the line - fixing it is expected to cost in the region of £10 million.
Engineers are currently surveying the damage caused by the 500,000 tonne landslip, which happened early in February.
It's one of the most complex projects they've faced, and they're currently using ground-penetrating radar to analyse movements at the embankment between the railway line and the River Eden.
They're warning the landslip is still active, and the embankment is still moving.
Network Rail is planning to build a concrete structure beneath the track to support it in the future.
The same section of embankment gave way in the 1870s while the Settle to Carlisle line was being built, and it took the Victorian engineers two years to repair.
While the stretch of line remains closed, a replacement bus service is transporting passengers between Carlisle and Appleby.