Police south of Auckland are busy re-directing traffic away from Auckland's southern motorway - all three lanes southbound are blocked near the Tacoma street off-ramp.

Motorists calling into Newstalk ZB say there's no way through and there are many people walking on the road lanes in front of the stopped traffic.

Police have confirmed the commotion is from a crash just after 9pm involving a motorcycle, it's not yet known what other vehicles may have been involved.

An ambulance has been called as a precautionary measure, but no injuries have been reported, the motorcyclist is believed to be standing up, and talking to police.