Highway maintenance teams are working to repair the collapsed culvert that had started to slump this week.
NZ Transport Agency senior network manager Chris Harris said crews noticed the culvert slumping and moved to make the highway single-lane yesterday and investigate the cause.
Repairs would take a week or more, and drivers had to build in extra time on their journey, he said.
"There was a significant void the size of a small car under the highway caused by water getting through and around a break in the culvert.
"We have backfilled that void as a short-term measure and are actively managing the key utility services with input from Delta, Aurora and Dunedin City Council."
He said the retaining crib wall would be secured and the back-filling would be completed.
"The site will be monitored throughout the weekend and crews would be back on Monday for a full and fairly significant repair.
"We appreciate everyone’s patience, slowing down and taking care at this site."
