Watch: Suspected tar balls on Sydney beaches actually poop-filled 'fatbergs'

Nov. 8 (UPI) -- Mysterious black balls that washed up on Sydney, Australia, beaches were initially suspected to be tar balls but turned out to be miniature "fatbergs" containing human feces.

The black balls were first spotted on Bondi Beach on Oct. 16, and similar balls were found on other city beaches in the ensuing days.

New South Wales environmental officials said they were initially suspected to be tar balls resulting from an unknown oil spill, but testing has now confirmed they contain cooking oil, soap scum, industrial chemicals, drug residue, hair and human feces.

Researchers said the balls are miniature "fatbergs," sewer-blocking accumulations of fat, grease and sewage.

"They smell absolutely disgusting, they smell worse than anything you've ever smelt," University of New South Wales Associate Professor Jon Beves, who led the investigation, told 9News.

He said the contents of the balls "pointed us to sewage and other sources of urban effluent" as their source.

Sydney Water said officials are not aware of any issues with the city's wastewater.

The New South Wales Environmental Protection Authority is continuing to investigate.