It's the second slip between the Haast Pass and the Gates of Haast this month.
The first followed a destructive storm on 10 September, which closed the road for nine days.
The Transport Agency says the latest slip is in the same area and is the result of heavy rain.
A spokesperson, Mark Pinner, says the road should reopen on Tuesday morning if the weather stays fine.
Mr Pinner says significant remediation of the hillside may be needed to prevent further slips.
