Nine popular swimming spots in Sydney’s Northern Beaches have been forced to close after more ball-shaped debris washed up ashore.

White and grey coloured balls were found scattered along the shores at Manly, Dee Why, Long Reef, Queenscliff, Freshwater, North and South Curl Curl, North Steyne and North Narrabeen beaches.

Northern Beaches Council has advised the public to avoid those beaches until further notice.

The NSW Environment Protection Authority (EPA) has been alerted and is working with council to collect samples for testing.

The EPA said it was testing the debris after first getting reports they had been found on Dee Why Beach.

“EPA officers have collected samples of the debris for testing,” the EPA said in a statement.

“Members of the public are advised not to touch the debris balls, which have a similar appearance to those that washed up on Eastern suburbs’ beaches in October last year and were found to consist mostly of fatty acids and petroleum hydrocarbons.”

Anyone who finds the debris is asked to contact their local council or EPA’s environment line on 131 555.

“So far, most samples identified are marble-sized with a few larger in size,” Northern Beaches Council said in a statement.

The balls will be safely removed from the beaches. 

Authorities are also inspecting other beaches in the area for any more debris.

It comes after black ball-shaped debris washed up ashore on Coogee Beach in October.

In the weeks and months that followed, more debris was found at Bondi, Bronte, Clovelly, Congong, Frenchmans, Gordons Bay Little Bay, Malabar, Pooles, Silver, Tamarama and 1080 beaches.

They were suspected to be “tar balls” — remnants of oil spills that ball up.

NSW EPA in December confirmed that testing on the debris that washed up on Sydney’s Eastern Beaches in October concluded its “origin is likely a source that releases mixed waste”.

Where the balls originated, however, remained a mystery.