Motorists should expect delays on State Highway 1, north of Auckland, after concrete panels fell from a truck.
A police spokesperson said the incident in the Dome Valley about 7.45am Thursday had blocked the northbound lane and half of the southbound lane.
While traffic could still get through, there would be delays, the spokesperson said.
No one was injured when the two concrete panels fell onto the road, but police were on scene and traffic management was being established.
The New Zealand Transport Agency said the fallen panels had blocked the lanes on Dome Valley near Forestry Rd.
"Contractors are en route and traffic management is likely to go in place," the agency said.
"Please avoid the area if possible or expect delays."