The U.S. Environmental Protection Agency is conducting a criminal investigation into a chain of industrial barrel refurbishing plants in Wisconsin, a whistleblower in the case has disclosed in court filings.

Will Kramer, who was a contractor examining safety in the plants before he went public with concerns about what he witnessed, wrote in court documents that he has been in contact with agents from the EPA's Criminal Investigation Division since March 2017.

The EPA agents have asked Kramer not to disclose their contact with him and not to share documents with other government entities, Kramer wrote in a court brief.

An EPA criminal investigative agent called Kramer again in August, asking him to withhold documents shared "as doing so could cause real harm to the EPA's ongoing investigation," Kramer wrote in the brief filed late last week.

Kramer honored EPA's request for months. He referenced the investigation in court filings in response to an effort by the company to obtain documents, audio recordings and other materials Kramer has provided to government agents. He also provided the materials to the Milwaukee Journal Sentinel, which published an investigation exposing dangers in and around the plants in February 2017.

Known locally as Mid-America, the plants are operated by Container Life Cycle Management, a joint venture majority owned by Greif Inc., a $3.3 billion Ohio-based firm. CLCM also operates plants in Arkansas and Tennessee.

The plants refurbish 55-gallon steel drums and large plastic chemical containers, cleaning them for reuse or recycling.

Greif filed the subpoena for records from Kramer as part of a lawsuit filed by residents living near the plant in St. Francis. A hearing in Milwaukee County Circuit Court in the matter is set for next month.

Federal agents were initially barred from entering the plants to investigate the reported dangerous conditions, prompting them to take the unusual step of securing a search warrant to get into the plants. Officials got the court-issued warrant because they were concerned they were not seeing true operations, as required under federal law.

EPA investigators who interviewed residents near the St. Francis plant reported feeling ill themselves, which they attributed to the plant's discharge.

Asked if the agencyhas an ongoing criminal investigation, an agency spokesman wrote in an email: "EPA can neither confirm nor deny the existence of any criminal investigation."

Representatives from Greif did not respond to emails seeking comment.

Workers at the plants told the Journal Sentinel that chemicals were routinely mixed together, triggering dangerous reactions that resulted in chemical and heat-related burns, injuries from exploding barrels, breathing difficulties and other health problems.

Residents near the St. Francis plant say it is often miserable living there. Fumes result in burning eyes, sore throats and headaches, forcing them to stay in their homes at times.

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The Journal Sentinel findings were based on 16 hours of audio recordings made by Kramer of employees discussing dangers in the plant; hundreds of pages of documents, including internal injury reports and safety audits; as well as public records and interviews with workers, regulators and experts.

Following the investigation, state and federal regulators recorded 70 violations at the plants in St. Francis, Milwaukee and Oak Creek. The EPA was among those agencies, but it has said nothing about the case since filing the violations early this year, prompting an August letter seeking an update by U.S. Sen. Tammy Baldwin (D-Wis.).

The EPA responded, saying it could not discuss enforcement actions before completion. The agency did say it had tested soil near the St. Francis plant and the agency does not believe there is "any immediate threat to human health or the environment."

The EPA letter also said the agency is working with the state Department of Natural Resources on the "appropriateness" of new pollution control equipment being installed at the St. Francis plant. The DNR has said the company does not need state approval to operate the new equipment.

Read the investigation

To read the Journal Sentinel's "Burned" investigation, into safety hazards at drum reconditioning plants, go to jsonline.com/burned.