Road authorities said the road is now fully reopened after two eastbound lanes were blocked as emergency crews worked at the site.
Motorists, however, are still being told to expect delays as congestion eases through the area.
FINAL UPDATE 8:55AM #SH18 has reopened again on the Greenhithe Bridge, following an earlier multi-vehicle crash. Expect delays as congestion eases through the area. ^MF https://t.co/OacNFgbsVy
— Waka Kotahi NZTA Auckland & Northland (@WakaKotahiAkNth) September 14, 2022
The circumstances of the crash are not yet known.
Earlier, witnesses said numerous fire engines and ambulances were on the bridge.