All lanes on Auckland Harbour Bridge have reopened but gridlock stretching more than 9km remains following a police incident.

Earlier, two northbound lanes were closed. The New Zealand Transport Agency (NZTA) said they reopened about 1.05pm and traffic should begin easing.

Bumper-to-bumper traffic trailed back from the bridge, through the Central Motorway Junction and onto the Southern Motorway to Greenlane as of 1.20pm, Google’s live traffic data showed.

NZTA said two lanes northbound remained open and people are urged to merge with care to pass.

“The Curran St on-ramp is now closed and drivers should expect extra travel time and long delays.”

Traffic is currently gridlocked from the bridge back to the Gillies Ave on-ramp, with the travel time for the 6.2km journey at 50 minutes.

Due to an incident on Auckland's Harbour Bridge, traffic has backed up to Gillies Ave.