Charges could be laid after a truck and digger crashed into an Auckland overbridge putting Auckland's main motorway into traffic chaos for several hours yesterday.

At 1.15pm, the arm of the digger struck the Penrose overbridge, causing the digger to be knocked off its trailer on to two of the three southbound lanes of the Southern Motorway.

Police today issued a thanks to those caught up in the chaos for their patience and promised anyone found responsible would be held to account.

Waitemata police road policing manager Trevor Beggs said yesterday was a "nightmare commute" home for many.

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"Police want to assure the motoring public that anyone found to be responsible for the crash and the resulting traffic disruption will be held fully to account."

He said it took a multi-agency effort to remove the obstruction and reopen the network.

"Everyone pulled together to get the job done in an incredibly short time under the circumstances."

Waitemata police were continuing to investigate the incident and are reviewing CCTV footage, talking to those involved and taking witness statements.