"It is believed smoke in the area from a suspected burn-off is causing significant visibility issues along SH2 and led to the crash," a statement said.
Diversions have been put in place because of the smoke.
Northbound traffic is being diverted onto Higginson St, and southbound traffic is being diverted up to Te Aute Trust Rd.
Fire services are said to be looking for the source of the smoke in the area.