Emergency services are working to free stranded motorists on State Highway 2 north of Gisborne, where two large slips tumbled onto the road on Thursday afternoon.
The Transport Agency says it's unlikely the motorists would get home for the night, so emergency services have been helping them find accommodation.
About 20 vehicles were evacuated by police after they got trapped between the slips, caused by heavy rain about 12 kilometres south of Matawai.
Police say an elderly man was injured after the slip pushed another vehicle into his.
The Transport Agency says the northern slip has been cleared but a larger slip to the south is still blocking the road. South of that slip, 23 road users have been stranded by flooding on the highway.
Two contractors' crews sent to clear the slip are among those stranded.
The highway will remain closed overnight; the agency will assess the remaining slip on Friday morning.
Napier-Wairoa highway reopened
Earlier in the day, State Highway 2 between Napier and Wairoa was reopened, though motorists were advised to be extremely cautious.
With more heavy rain hitting the region on Thursday evening, MetService warns that flash flooding could recur, especially in low-lying areas, and that further slips are likely.
A series of slips on Wednesday night - from the Matahorua Gorge to Tangoio, just north of Napier - left Gisborne cut off by road for much of Thursday morning.
Up to 200 millimetres of rain fell in the Gisborne area in 24 hours, forcing the evacuation of up to 40 people from 18 homes north of Tolaga Bay on Wednesday.