Police are responding to reports of a motorcyclist crashing into a bridge at Pohuehue.
Police were called to the incident on SH1 south of Warkworth at 7.14am.
A police spokeswoman said the motorcyclist had been seriously injured.
The southbound lane is closed and a stop/go sign is in place. NZTA has advised that motorists should expect long delays or avoid the area.
Congestion on SH1 has slowed to a crawl between the Valerie Close intersection and Pohuehue Falls.