Crews clearing a massive slip blocking State Highway 1 south of Kaikoura are attempting to stabilise the rock face 100 metres above the road.
The Transport Agency estimates as much 30,000 cubic metres of debris came down in the slip at Peketa, about 15km from Kaikoura on Friday, covering the rail line and main highway.
The Canterbury state highways operations manager says stabilising the rock face is a huge task which must be carried out carefully, so as not to endanger the crews clearing the slip below.
Peter Connors says the work is on track to re-open at least one lane of the highway by Thursday and crews will continue to work around the clock until the slip is cleared.
A detour to Christchurch via Route 70 is available for light vehicles, but heavy trucks must take State Highway 7 through the Lewis Pass.
Meanwhile, KiwiRail says it still has 50 containers of delayed freight to move.
Chief executive Jim Quinn told Morning Report on Tuesday the company has moved 142 delayed containers by road or ship, including all those with perishable goods.
Work will begin on assessing the condition of the railway line on Thursday.
