Mysterious debris balls found on beaches along the New South Wales Central Coast in August likely originated in Sydney, the state Environment Protection Authority says.

Samples of the Central Coast balls were collected for comparison with samples from different wastewater treatment facilities operated by Central Coast Council, Hunter Water and Sydney Water.

The August balls matched the chemical signature from Sydney Water’s Malabar Wastewater System, making it the most probably source.

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.Mysterious debris balls were found on Central Coast beaches in August. (Central Coast Council )

Sydney Water is now investigating to further pinpoint the source within that system.

Work is already underway to prevent repeated incidents in the short term, with medium- and long-term projects to go ahead as well.

The EPA will provide further updates when they are available.