The New Zealand Transport Agency warned motorists to expect delays.
"Emergency services are on site. Please delay your journey or use an alternative route," NZTA said on its website.
Northbound drivers can take Kaiwaka-Mangawhai Rd, onto Moir St, left onto Molesworth Dr, left onto Mangawhai Heads Rd, right onto Cove Rd, before continuing through Waipu and back to State Highway 1.
Due to a crash SH1 is CLOSED north of Kaiwaka. A detour is in place via local roads. Expect heavy traffic in area & delay travel if poss ^LC pic.twitter.com/BAydBSCCH8
— Waka Kotahi NZTA Auckland & Northland (@WakaKotahiAkNth) April 26, 2017