State Highway 1 is closed in both directions near the Auckland-Waikato border after a large truck rolled.
The closure is in place between Mill Rd and Beaver Rd in Bombay, and Waka Kotahi NZTA warns motorists to "expect long delays" in the area.
Northbound traffic is being detoured via Beaver Rd, Jericho Rd, and back onto the motorway via Mill Rd, NZTA says. Southbound traffic is being detoured off at Mill Rd, onto Razorback Rd, and Beaver Rd East.
At 5:15pm on Tuesday, NZTA says they received reports of a crash blocking southbound lanes of the Waikato Expressway, and by 6:30pm a full motorway closure was in place.
NZTA asks drivers to consider avoiding this area of SH1 on Tuesday night if possible. Once vehicle recovery is complete, a clean-up will begin.