Nine beaches in Sydney, including well-known Manly beach, were closed to bathers on Tuesday after small white and grey balls of debris washed up on the shores at the height of the summer holiday season.
Northern Beaches Council said it was working on safely removing the matter. Most of the samples of the ball-shaped debris were the size of marbles, with some larger, it said in a statement.
Sydney's ocean beaches, famed for golden sand and clean water, draw tourists from around the globe.
Beachgoers were advised to avoid Manly, Dee Why, Long Reef, Queenscliff, Freshwater, North and South Curl Curl, North Steyne and North Narrabeen beaches until further notice and keep away from the material while the clean-up and investigations continued.
Authorities said they were working closely with the state's environmental agency to collect samples of the debris for testing.
Last October, several beaches including the iconic Bondi east of downtown Sydney were shut after thousands of black balls appeared on the shores.
An inquiry later found that those balls were formed from fatty acids, chemicals similar to those in cosmetics and cleaning products, as well as hair, food waste and other materials associated with wastewater.
