New Zealand Transport Agency maintenance contract manager for the West Coast Moira Whinham said yesterday a geotechnical engineer on site had carried out a preliminary assessment of the rockfall and "agreed it is not straightforward to remedy today''.
It was expected it would take longer than originally thought for abseilers to remove loose material from the rock face.
The rockfall, blocking both lanes, was thought to have been triggered by recent rain and rain continued to slow progress yesterday.
Clarke Bluff is a narrow point on State Highway 6 just west of the Gates of Haast and has had rockfalls in the past.