Hundreds of enigmatic black tar-like balls have appeared on two popular Sydney beaches, leading lifeguards to close the shores to swimmers.

“Mysterious, black, ball-shaped debris” started washing up on Coogee Beach on Tuesday afternoon, leaving Australian authorities puzzled and working to determine their origin.

Black, ball-shaped debris washes ashore on Sydney’s Coogee Beach prompting closure and investigation by Randwick City Council pic.twitter.com/ktrGzxzK7v

Hundreds of golf-to-cricket-ball-sized spheres could be seen scattered along the coast, usually busy with Sydneysiders and tourists.

However, only a few seagulls wandered among the spheres, pecking and inspecting them.

The balls were also found at Gordon’s Bay nearby, a popular snorkeling and fishing spot that was also shut down.

“At this point, the material is unidentified,” Mayor Dylan Parker stated in a social media post. “They may be ‘tar balls’ formed when oil interacts with debris and water, often resulting from oil spills or seepage.”

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