More debris is expected to wash onto beaches along the New South Wales coastline after a cargo ship lost 83 containers.

Sanitary products have washed up on the New South Wales coastline after the ship encountered extreme weather. ( ABC News )

Nappies, sanitary products and surgical masks have already washed ashore after the Liberian ship lost its cargo in extreme weather on Thursday.

New South Wales Roads and Maritime Services executive director Angus Mitchell said the containers were believed to have fallen overboard from the 268-metre YM Efficiency about 30 kilometres off the coast of Port Stephens in Commonwealth waters.

Roads and Maritime has advised people boating off the NSW north coast to "be on alert for debris". ( Supplied: RMS )

He said ships had been known to lose cargo in the past.

Roads and Maritime advised anyone boating off the north coast this weekend to "be on alert for debris" after the containers toppled from the cargo ship.

The YM Efficiency is a 268.8 metre container vessel registered in Liberia. ( Supplied: Joe Becker, MarineTraffic )

Two containers from the 83 that fell have already been sighted about 100 metres offshore from Fingal Bay and Boondelbah Island near Port Stephens.

"A full manifest of the cargo on board the vessel and the condition of the vessel is being sought," Mr Mitchell said.

Another 30 containers onboard the vessel were reported to be severely damaged.

Recovery and removal of these containers is the responsibility of the vessel operator.

Aerial view of the 12 metre shipping containers beginning to fall off the YM Efficiency. ( ABC News )

Boaters were being made aware of possible navigation hazards on marine radio.

Members of the public should report any sightings of the 12-metre containers to the Australian Maritime Safety Authority reporting hotline on 1800 641 792.

Roads and Maritime said it was working with the AMSA and the vessel's agents and insurers to ensure the safest recovery of the containers.

Steven Ka, a spokesman for the YM Efficiency, confirmed that the crew are safe and no one was injured.

He noted that there was no damage to the ship itself, which is still sailing towards Port Botany.

The ship is currently located 12 nautical miles off the coast of the Northern beaches. It was expected to dock this afternoon, as authorities wait for improved weather.