A railway line in Gwynedd is to stay closed after it was damaged during Storm Doris.
Engineers have been working to repair the line after a large tree fell onto the track between Llanrwst and Blaenau Ffestiniog on Thursday.
But the work has unveiled an unstable rock formation directly next to the track which requires further attention.
Network Rail said it would be "unsafe" to reopen the line on Monday as planned.
Arriva Trains Wales will operate a shuttle train service between Llandudno Junction and North Llanrwst, with a bus replacement service in place between Llanrwst North and Blaenau Ffestiniog.
Andy Thomas, Network Rail's route managing director for Wales, said: "Passenger safety is our absolute priority and our repairs have revealed significant damage to the embankment which only became apparent when work started.
"We are working with Arriva Trains Wales to minimise the disruption to passengers and we apologise for the inconvenience this has caused.
"We will provide more updates on when the line can reopen in the coming days when the weather conditions improve."