NZTA Central Otago area manager John Jarvis said the big rocks broke loose from the Remarkables about 1km above SH6.
"At least three rocks made it to the road. Another couple got caught part way down the slope, but are safely tucked in behind older rocks on the slope so there's no risk of them coming further down."
He said the main mass of material was "sitting on a flattish gully up the top and is unlikely to progress much further down the slope and will vegetate over time."
There did not appear to be any immediate risk of further rockfalls in this area.
Mr Jarvis said other boulders were dotted around the hillside, which indicated there had been similar falls in the past.
He said it was unlikely catch-fences would have stopped the boulders which pockmarked the road with impact craters on Saturday, closing the road from 7am until just after 10am.
The area above Saturday's rockfall would be inspected in the next few weeks as part of NZTA's routine aerial checks of the Nevis Bluff on SH6 between Frankton and Cromwell.
"We'll do a helicopter flyover and see if there's any changes, but we don't believe there's anything hanging up there of any immediate risk," he said.
The NZTA would continue to monitor the site as road-user safety was "paramount".
• On Monday the Otago Daily Times reported a rockfall closed the road at the Devil's Staircase in September 2000. This fall did not happen at the Devil's Staircase but at the Nevis Bluff on SH6 between Frankton and Cromwell.
