State Highway 1 at Maheno is down to one lane after a truck and trailer unit rolled this morning.
Emergency services were called to the crash about 9.40am. Fuel from the truck and trailer unit had spilled on to the road, a police spokeswoman said.
"It's a truck and trailer unit which is on its side,'' she said.
"The truck is blocking the northbound lane, but the trailer is in the ditch.''
Traffic management was in place, and the southbound lane remained open.
The driver sustained minor injuries.
Fire crews from Kakanui, Weston and Oamaru are in attendance.
