Investigations are under way after at least 40 shipping containers fell overboard off the Illawarra coast on Sunday.
At about 6.10am the Singapore-flagged container ship APL England lost power in heavy seas several kilometres off the Illawarra coast.
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While power was restored a few minutes later, the seas had caused the ship to roll heavily. As a result container stacks collapsed and 40 containers fell overboard.
As the water was around two kilometres deep there is little chance of them washing up on the shore, or posing a danger to shipping.
The ship's master has reported six other containers were protruding off the starboard side and a further 74 containers were damaged in the heavy seas.
The Australian Maritime Safety Authority dispatched a jet to fly over the waters to see if any containers could be spotted.
The ship was heading to Melbourne but has turned around and is now heading to Brisbane.
The authority will inspect the ship upon its arrival.
The Australian Transport Safety Bureau has been notified and will investigate the incident.
In August 2016 the same ship lost 37 containers in the Great Australian Bight due to heavy rolling in rough seas.