The operators behind REDcycle may face a possible fine of more than $165,000 after being charged by the environmental protection watchdog investigating the botched soft plastic recycling program.

On Friday, the Environment Protection Authority (EPA) Victoria said RG Programs and Services had failed to provide information about the locations of warehouses secretly stockpiling hundreds of millions of bags.

The operators have been charged with three counts of failing to comply with an information gathering notice. The maximum penalty for the fine is more than $165,000.

About 3,000 tonnes of soft plastics meant to be recycled were found earlier in December across six sites as part of the investigation into the suspended program, posing potential fire risks.

It equated to around half a billion plastic bags.

A notice issued to the scheme’s operators led investigators to the six warehouses, managed by logistics companies in Melbourne’s western and northern suburbs.

The EPA said the notice issued to RG Programs and Services required information to be disclosed by the program’s operators on the locations and amounts of stored soft plastics.

It was issued following the discovery in May that soft plastics had been stored in a Williamstown North warehouse instead of being recycled.

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“It is alleged RG Programs and Services Pty Ltd only provided partial information of known storage sites in response to the Information Gathering Notice,” the EPA said.

“Additional information was obtained through investigations by EPA officers, including working directly with trucking and logistics companies.

“EPA is not satisfied there is a reasonable excuse for this non-disclosure, leading to the charges today.”

The REDcycle program was suspended in November after the Age reported soft plastics dropped off by customers at Coles and Woolworths were being stockpiled rather than recycled.

Drop-off points at the supermarkets, which had been collecting more than 5m pieces of soft plastics every day, were swiftly closed.

REDcycle said the two companies that took the recycled material couldn’t accept any more material, with a fire in a factory and “downturns in market demand” blamed.

“Consumer recycling of soft plastic has grown exponentially in recent years, with a 350% increase in plastic returned since 2019,” a REDcycle spokesperson said at the time.

“However, due to several unforeseen challenges exacerbated by the pandemic, REDcycle’s recycling partners have temporarily stopped accepting and processing soft plastics. This combination has put untenable pressure on the REDcycle business model.”

Environment minister Tanya Plibersek called on the supermarket chains to come up with a “viable solution” after they were forced to hit pause on the scheme.

On Friday afternoon, the EPA confirmed an additional manufacturing site located in Dandenong South was safely storing material from the REDcycle program.

Previous storage sites were confirmed across Tottenham, West Footscray, Truganina, Williamstown North, Campbellfield, Tullamarine, Dandenong South and West Wodonga.

EPA CEO Lee Miezis said the body would continue inspecting sites into the holiday period and beyond.

“Our officers have been working hard to ensure risk control measures are put in place by those responsible and our environmental laws are being complied with,” he said.

“It is important for local communities and the environment that these businesses store the material safely.’’

The EPA investigation is ongoing, with the possibility of further charges for breaches of environmental laws, including waste duties.

Guardian Australia sought comment from REDcycle.