Police said they did not believe anyone had been injured in the crash, which took place about 2.30pm.
Northbound traffic was being diverted at McNamaras Rd, through Parsonage Rd, Waimate Hunter Rd, and Lower Hook Rd. Southbound traffic was being directed off SH1 at Lower Hook Rd.
Motorists were asked to take extra care while the diversions were in place and avoid the area if possible.