NZ Transport Agency Waka Kotahi advised of the crash, on State Highway 1 at Burnside, near the northbound Main South Road on-ramp, about 7.25am.
A witness said the crash involved two trucks heading up the hill towards Lookout Point.
Initially, the northbound left lane of the motorway was closed but just before 9am NZTA said the right lane was also being closed to allow for vehicle recovery.
In an update at 10.25am NZTA advised that both lanes had reopened, but traffic had been "heavily impacted" and motorists could still expect delays.
Traffic was reportedly backed up as far as Mosgiel at one stage, and motorists were being diverted on to Kaikorai Valley Rd.
Police said no injuries had been reported.
Orbus earlier said the accident caused delays to some of its services. The affected routes were 77, 78 and 40.
Otago Regional Council compliance manager Simon Wilson said the council was notified of the incident.
“Our team responded but there was no pollution and no action was required.”
