A major Auckland motorway was blocked for a period this afternoon as armed police arrested a man for allegedly making threatening comments on social media.

Police said a vehicle of interest was found travelling on State Highway 20B and stopped by officers who were armed as a precaution. Both occupants of the vehicle were taken into custody without incident.

"A man is being spoken to by police in relation to non-specific threatening comments made on social media earlier today," a police spokesperson said.

Charges were being considered, they added.

"Police acknowledge motorists' cooperation, as a lane was briefly blocked to allow our staff to carry out their work safely."

NZTA said an eastbound lane was closed on State Highway 20B due to a "police issue" at around 4.30pm.

The lane reopened, and all vehicles were moved by 5.15pm, a spokesperson said.