A hole in a bridge has closed a section of State Highway 53.
The bridge, which goes over the Tauherenikau River between Featherston and Martinborough, was shut just before 3pm today.
The hole is an estimated 75cm wide.
The New Zealand Transport Agency (NZTA), which manages the state highway, said heavy rain last Friday raised water levels in the Tauherenikau River, undermining the road near the bridge.
NZTA was notified to the washout today.
After a structural assessment by engineers, contractors will start repairs.
South Wairarapa District Council infrastructure and services group manager Mark Allingham said Fulton Hogan and NZTA were on site promptly, evaluating the bridge.
He could not confirm when the road would be reopened but said it would most probably remain closed tomorrow.
A detour route is available via State Highway 2 and Number 1 Line.
Handley Thompson, chairman of the AA Wairarapa District Council, said he went down to have a look after hearing of the problem.
"This one hasn't been on our radar," Thompson said, noting that the Waihenga Bridge, over the Ruamahanga River, was more often a cause for concern.