There were no injuries but the motorway was closed for a period causing major delays after the crash at Burnside about 7.15am.
"One truck in the right-hand lane driven by a 58-year-old male, changed lanes to the left lane and has crashed into another truck driven by a 43-year-old male," Senior Sergeant Anthony Bond said.
The commercial vehicle team was investigating the crash, he said.
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.
A crane was brought in to remove one of the trucks.
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.”
