State Highway Six near Haast on the West Coast has one lane open, after being closed for most of the day because of rockfall.
The Transport Agency says large boulders blocking the road 1km west of Clarke's Bluff have been blown up with dynamite and partially cleared.
The biggest boulder was described as the size of a house.
Agency spokesperson Mark Pinner says the road may have to be closed again overnight on Friday while more clearing is done, but would be opened again Saturday morning.
Mr Pinner says both lanes could be open on Saturday if all goes to plan.
He says a geotechnical engineer is assessing the safety of the rockface above the road.