The mysterious balls that forced the closure of several beaches in Sydney last week were found to contain saturated acids, E. coli and faecal bacteria, authorities say.
Sydney’s Northern Beaches council said it has sent the debris to the New South Wales Environment Protection Authority (EPA) for further analysis.
Nine beaches, including popular spots Manly and Dee Why, were closed on 14 January after the marble-sized balls started washing up.
It came months after thousands of black blobs started appearing on the city’s coasts in October, prompting authorities to close some of its most famous beaches for several days and order a massive clean-up.
The latest batch of balls was cleaned up from harbour beaches this week, the Northern Beaches council said in its statement on Tuesday.
It urged anyone who spotted the balls not to handle them and to contact authorities.
Besides the acids and bacteria, the balls also contained volcanic rock pumice.
Northern Beaches mayor Sue Heins said she hopes the EPA analysis will “identify the source so that they can stop this from happening at other beaches”.
“We are continuing to conduct regular inspections of our beaches and encourage the community to report any sightings,” she said.
The first batch of debris in October were at first mistakenly called “tar balls” but were later found to contain everything from cooking oil and soap scum molecules, to blood pressure medication, pesticides, hair, methamphetamine and veterinary drugs.
Scientists said they resembled fat, oil and grease blobs – often called “fatbergs” – which are commonly formed in sewage systems.
But Sydney Water has reported that its water treatment plans are operating normally and that there were no known issues with waste systems in the city.
