Reports from the community have led the Environmental Protection Authority to consider an investigation into the cause of the materials on Shelly Beach, an EPA spokesman said.

Good Nurdle Hunting leader Colleen Hughson, who with other volunteers removed about 500 of the white waxy balls, said she suspected an outfall from the Warrnambool Sewage Treatment Plant was to blame.

But Wannon Water managing director Andrew Jeffers said he was confident the material did not come from the treatment plant after a nurdle spill led the water authority to install a screen in 2017 to prevent solid materials flowing into the ocean.

Mr Jeffers said the plant had operated "as normal and there have been no unusual events".

"What we can control is how the plant is working now and into the future, and we can be sure the discharges are not happening now," he said.

Ms Hughson said fat balls, a combination of oil, wipes and hair, had appeared previously this year in rock pools but not along the beach's tide lines as they had on Saturday.

"They smell rancid," she said, adding she witnessed a similar incident in October last year. "We have had them tested before and there are a number of different fats in there. There are often clumps of human hair in there that would indicate they have come from a drain."

Mr Jeffers said the treatment plant screens were monitored and cleaned daily, after collecting up to 40 fat balls.

"This monitoring has not identified any unusual activity or increase in the number of solid materials, including fat balls," he said.

Mr Jeffers said the screens collected organic material and "a minimal amount" of fats, fruit stickers, cotton buds, nurdles, other small plastics and sanitary products.

He said a new $2.2 million automated screen would soon also be installed to remove a need for manual cleaning.

Ms Hughson said some of the materials found on beaches could pre-date the water authority's installation of a screen, but believed others were recently deposited.

"I wouldn't say the fat balls are historical, but some of the plastics are historical," she said.

"I have said in my discussions with Wannon Water that there are still fresh ones coming up."

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