A rock fall has blocked access to Queenstown on State Highway 6 via the Kawarau Gorge between Cromwell and Queenstown.
The rock fall was reported at 6.30am and traffic was reduced to one lane until the road was closed completely at 2pm.
New Zealand Transport Agency Central Otago manager John Jarvis said a large rock had fallen onto the road, but more rocks were slowly moving downwards and they were now hanging above it.
"We're trying to bring the whole block of rock down," he said. If the rock could not be brought down by 5pm, the road could be closed overnight for safety reasons.
The rock fall was caused by the heavy rain in the area over the past few weeks. There were other less serious rock falls in the area, including one between Frankton and Kingston, and one in Lindis Pass.
There is a detour for motorists travelling to Queenstown via the Crown Range between Wanaka and Queenstown, so the holiday resort town is not completely isolated.