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.

Sydney’s popular Manly Beach and other beaches around the Australian city were closed on Tuesday as authorities investigated marble-sized balls of white and gray debris that had washed on shore, in the latest such mysterious incident in recent months.

Workers have cleaned up and reopened seven of nine northern Sydney beaches after mysterious balls washed ashore.

All but one of the nine major north Sydney beaches which were closed this week after mysterious ball shaped debris washed up on the sands have now reopened.

Beaches in Sydney, Australia, were closed to bathers after small white and grey balls of debris washed up on the shores at the height of the summer holiday season.

Swimmers and surfers were urged out of the water on Tuesday afternoon after the white-grey, ball-shaped debris was found along Sydney's northern beaches.

The Northern Beaches Council said that efforts were underway to safely remove the debris. Meanwhile, Local authorities collaborated with the state’s environmental agency to investigate the matter.

Sydney’s popular beaches, including Manly, were closed after marble-sized white and grey balls of debris were discovered washing ashore. This marks the latest mysterious incident in a series of similar occurrences in recent months.

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The discovery of the marble-sized balls comes after a similar incident in October closed Sydney's Bondi Beach, among other tourist hotspots.