The Napier-Taupō Road is closed following a serious crash in Hawke's Bay north of Napier.
Police were called to the scene near Beattie Rd and Ellis Wallace Rd after reports of a truck and trailer flipping shortly before 5am.
There are no reports of injuries but officials say State Highway 5 is expected to stay closed for some time.
"Light vehicles will be diverted down Seafield Rd and onto Glengarry Rd," police said in a statement.
"Heavy vehicles will need to seek alternative routes."