"This will continue for several days so crews can remove the remaining slip material and make the highway safe for two lanes of traffic again," Ms Wright said.
"People need to factor in extra time for this journey until we have both lanes safely reopened."
Kiwi Rail said it was hoping to reopen the Midland Line on Wednesday, although that was highly weather dependent. The Tranz Alpine passenger service is currently operating a daily return service from Christchurch to Arthur's Pass.
Intercity will put on a temporary bus service from tomorrow, through the Lewis Pass.
As the power lines were also taken out by the slip, the railway crossing warning lights in the Otira to Jacksons area are not operating and Kiwi Rail will be manually controlling these crossings when the trains resume.
"Slow down and be prepared to stop at all level crossings," Ms Wright said.
- Greymouth Star