Debris balls that closed nine northern Sydney beaches last week contained faeces, E. coli Test results showed bacteria and saturated fatty acids.

Northern Beaches Council said on Tuesday it had received further analysis of the balls sent to the NSW Environmental Protection Agency (EPA) for testing.

“In addition to the hydrocarbons identified in last week’s preliminary test results, the latest results also indicate the presence of saturated fatty acids as well as fecal coliform and E. coli," the committee said in a statement.

Hydrocarbons are organic compounds found in petroleum and gasoline.

Manly, Dee Why, Long Reef, Queenscliff, Freshwater, North and South Curl Curl, North Steyne and North Narrabeen beaches were temporarily closed last week after the ball washed ashore.

Northern Beaches Council said it understood the EPA had taken its own ball samples for analysis and the results would be compared with those collected by the council.

The council said "small numbers" of marble-sized balls "mixed with pumice" were found and cleaned up at other harbor beaches this week, including Little Manly Beach and the West Esplanade.

Northern Beaches Mayor Sue Heins said she hoped "the EPA's analysis will identify the source so they can stop this happening on other beaches".

"We will continue to conduct regular beach checks and encourage the community to report any sightings," she said.

The sticky round spheres have been found on many city beaches over the past six months, forcing some to temporarily close.

As Guardian Australia reported over the weekend, some experts and observers believe Sydney's unusual sewage system is to blame.

Thousands of black balls washed up on beaches in the eastern suburbs including Bondi, Bronte, Coogee and Tamarama last October.

The balls were initially widely reported as "tar balls" composed of crude oil until testing coordinated with the U.S. Environmental Protection Agency showed they were consistent with human-generated waste.

The EPA said it could not determine the source.

But Stuart Khan, dean of the University of Sydney's School of Civil Engineering and a water policy expert, said: "We know it's a wastewater source."

Sydney's sewage is only treated "primarily" at the sewage treatment plants in Bondi, Malabar and North Head, and then discharged into the sea through "deepwater outfall" pipelines 2 kilometers to 4 kilometers from the coast.

Primary treatment involves physical processes, such as pumping sewage through screens to remove solid waste. Secondary treatment - not used at the Bondi, Malabar and North Point plants - involves more refined filtration and biological treatment to break down the effluent.

Sydney Water says its water treatment plants are operating normally but plans to upgrade the city's wastewater network over the next 10 years.