A large grass fire on the side of State Highway 1 near Domett, north of Christchurch, closed the road before firefighters could get the blaze under control.
Fire and Emergency New Zealand spokesman Ian Littlejohn said the communications centre began fielding multiple calls on the fire just after 2pm.
Five crews and two helicopters were called the scene about 500 metres north of Mainline Station Cafe near the intersection with Hurinui Mouth Rd.
Littlejohn said it took 40 minutes to contain the fire and crews remained at the scene.
The state highway was closed for a period but Littlejohn said it had now reopened to one lane.
"We are advising motorists to be careful."
He said there was a possibility of smoke nuisance causing vision problems for drivers and there were a number of bends in the road at the point.
Otherwise there was no risk to members of the public or buildings.
Littlejohn said conditions were extremely dry in the region and he expected a total fire ban would be implemented at midnight tonight.
Earlier the NZ Transport Agency sent out an alert on the incident asking motorists to avoid the area.