Police said they were alerted to the two-vehicle crash on SH1 near the intersection with Mile Flat Rd about 7.30am.
The crash involved two trucks, police later confirmed.
A Hate Hone St John spokesperson said one ambulance, one prime responder, one helicopter and one operations manager attended the scene.
One patient was assessed and transported by helicopter to Dunedin Hospital in a critical condition, the spokesperson said.
A witness at the scene said traffic was lined up for 5km either side of the closure.
He said the crash occurred between a bulk carrier truck and a logging truck and trailer unit.
One power pole was damaged in the crash, logs were strewn all over the road, and the front of the bulk carrier truck was severely damaged.
The road was closed all morning, although partially reopened with one lane operating and traffic management allowing cars through in both directions, police said in an update about 12.10pm.
NZTA said the road had been closed between SH1's intersections with Mile Flat Rd and Findlays Rd.
It fully reopened by about 3.35pm.
Motorists were warned of continued delays in the area.
- Allied Media
