Debris balls have washed up on several NSW beaches again, but authorities are unsure whether they are related to the ones that were previously found along dozens of Sydney beaches.

The Central Coast Council confirmed the balls were found at The Entrance Beach, Grant McBridge Baths, Blue Bay, Toowoon Bay, North Shelly Beach, Shelly Beach and Blue Lagoon Beach.

The Grant McBride Baths have been temporarily shut.

Beachgoers are advised to avoid going to the affected sites and not to touch the debris.

The debris balls are grey-coloured, ranging in size from one to four centimetres.

The NSW Environment Protection Authority (EPA) was first notified by a beachgoer who stumbled upon the balls at North Shelly Beach.

Council has since cleared all visible balls from that beach. 

Samples have been collected for testing, but the composition and source of the material are not yet known and could be from a variety of sources, like stormwater, sewerage or ships.

According to council, it is unclear whether these debris balls are related to the ones that washed up on Sydney beaches from October to January.

Investigations and clean-up are currently ongoing.

Council is managing the matter, but the EPA has offered to help if needed. 

“Council also advised they will continue monitoring beaches and will send samples of the debris balls for testing,” an EPA spokesperson said. 

“Further actions will be considered once test results are received.”

Black-coloured debris balls first appeared in Coogee, in Sydney’s east, in October before dozens more started popping up along the coastline up until January. 

The definite source still has not been determined.