Northland police and the Kaiwaka Volunteer Fire Brigade are also in attendance.
Motorists can expect delays of 30-40 minutes as SH1 has been closed between Kaiwaka-Mangawhai Rd and at Mangawhai Rd in Te Hana.
Waka Kotahi NZ Transport Agency reported the section of SH1 is likely to remain closed for some time as a serious crash investigation is expected to occur.
Diversions are in place with northbound traffic about to turn right to Mangawhai Rd after Te Hana, left to Tomarata Rd, on to Insley St, left to Moir St and follow Kaiwaka Mangawhai Rd to return to SH1 at Kaiwaka.
Southbound traffic can complete the same diversion in reverse.
Further updates are expected.