Authorities initially feared these balls could be made of toxic tar. Further testing from scientists indicated they are closer to 'fatbergs' typically found in sewers.

Scientists confirm ‘disgusting’ composition of mysterious tar balls that surfaced on Sydney beaches

The black balls which shut down beaches in Sydney last month and stumped authorities are “disgusting” lumps of human faeces, drugs and PFAS chemicals, according to detailed analysis by researchers.

Initial reports suggested they were made of tar and could have come from an oil spill or waste from a ship, but a plethora of tests have revealed they are more similar to “fatbergs”, commonly found in sewage systems.