A truck breakdown on the M1 Pacific Highway at Berowra has caused a 15-kilometre traffic jam, with south-bound traffic initially queued past the Mooney Mooney Bridge.

The truck was cleared at about 6.30am on Monday, but commuters were warned to expect delays throughout the morning peak.

Traffic queued back on the Mooney Mooney Bridge after a truck breakdown. Photo: Live Traffic NSW

The truck broke down near the Berowra exit just after 4.30am on Monday, blocking one south-bound lane.

By 8am conditions had eased and commuters were enjoying a smooth run from Mt White through to Berowra.

However, heavy traffic still stretched from Mount Colah to Wahroonga as commuters exited the motorway.

Commuters were told to expect significant delays and allow plenty of extra travel time.