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.

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.

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.

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

Testing by authorities determined those balls were most likely the result of a sewage spill. In a post on Facebook on Tuesday, the Northern Beaches Council said they were alerted

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.

But repeated occasions where wastewater is causing pollution and with no clear source must be addressed by the pollution watchdog and Sydney's water authority, Greens environment spokeswoman Sue Higginson said.

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.

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