A Hato Hone St John spokeswoman said one person in a minor condition was assessed and treated.
One ambulance, two rapid response units and one operations manager were sent to the scene.
The slip was covering both lanes.
A New Zealand Transport Agency spokeswoman said contractors were at the slip and had started clearing.
“Due to incoming weather and other safety concerns SH2 will remain closed between Waiotahi Valley Back Rd and Paerata Ridge for slip clearance tonight and throughout tomorrow, Tuesday.”
Detour details
For east bound traffic: Right on to Waiotahi Valley Back Rd, Verrall Rd, left at Paerata Ridge Rd before rejoining SH2. Westbound traffic in reverse.
The detour was not suitable for heavy vehicles.