Early on Tuesday, a 30m-40m section of a cliff collapsed on to the Livingstone-Duntroon road between State Highway 83 and Settlement Rd.
The site was assessed for safety risks by drone and a geotech engineer had a look on Tuesday.
A Waitaki District Council spokesman said it was unknown how long the road would remain closed.
"There are currently a number of precarious boulders and sections of rock remaining with the potential for further slips and falls.
"With that in mind, simply clearing the material on the road would not be appropriate until the causes have been determined, and action taken to secure or remove the remaining collapsed boulders and rock."
The fall was not caused by a rainfall event, or by geological activity such as a quake or tremor, he said.
Road traffic is encouraged to take the Georgetown-Ngapara road as a diversion to reach areas usually accessible by the Livingstone-Duntroon road.
The cliff is owned by Ngāi Tahu and the land behind it privately owned.
It is also close to one of the Unesco Whitestone Geopark sites.
Council, stakeholders and contractors are partnering with Ngāi Tahu to assess any historic or cultural significance, and preserve any carvings or rock art within the fall area, the spokesperson said.
The Alps 2 Ocean cycle trail has been diverted along Earthquakes Rd to rejoin the trail beyond the rock-fall site.
