Emergency services are in attendance at a single vehicle crash on State Highway 20 near Māngere.
Police were alerted to the crash, at the intersection of SH20 and SH20A, at around 12.10pm.
Initial indications suggest one person sustained critical injuries.
Two northbound lanes are blocked prior to the Walmsley Road over bridge, and traffic is building.
Motorists are advised to expect delays.
The Serious Crash Unit is in attendance.
ENDS.
Frankie Le Roy/NZ Police.