Officers were called to the incident about 10.40am and found the digger blocking multiple lanes.
A witness said a southbound Cargill Contracting truck appeared to have lost a wheel and hit the concrete median barrier.
“The digger that it was carrying has toppled off the side of the truck over the barrier into the northbound lane,” the witness said.
The motorway was blocked in both directions for a time, and traffic was being diverted at the Main South Rd off-ramps, into Concord and Kaikorai Valley Rd.
The digger was removed and the motorway reopened around 1.40pm.
Anyone with dashcam footage or who witnessed the incident was urged to contact police through 105 and reference event number P066019039.
About 2pm NZ Transport Agency Waka Kotahi advised that the motorway had reopened in both directions, but urged motorists to take care as congestion eased.
Two ambulances, three police vehicles and a number of fire appliances attended.
No injuries were reported.
