The swinging door that has become the Haast Pass was open again this morning after yet another closure yesterday.
The NZ Transport Agency says further closures are expected with more rain forecast.
State highway 6 reopened this morning to all traffic from Haast to Makarora after being closed since midday yesterday after heavy rain.
NZTA performance manager Pete Connors said about 40mm of rain fell in the Haast Pass area yesterday, bringing a small amount of rock and gravel down on to the highway, which was cleared away today.
"The rain eased to drizzle overnight and with less movement at the Diana Falls slip this morning it is again safe for motorists to travel through the area,'' Mr Connors said.
The slip sat within a "challenging'' geological site and coupled with the forces of nature, it had proved difficult to stabilise and manage, he said.
"As a result, there will be continued uncertainty with access along this section of State highway 6 when there is heavy rain and this situation is expected to remain for some time yet.''
The highway will continue to be closed to all traffic from 6pm to 8am every day as a safety precaution.