UnitedHealth Group shares fell about 2% in trading Wednesday morning after the Wall Street Journal reported new details on a previously reported criminal investigation by the U.S. Department of Justice into Medicare Advantage billing practices at the Eden Prairie-based health care giant.

The Justice Department’s criminal health care fraud unit is investigating how UnitedHealth Group deployed doctors and nurses to collect diagnosis data to boost government payments, according to the Journal’s report, which cited people familiar with the matter.

Former UnitedHealth employees say they’ve been questioned by prosecutors working for the health care fraud unit in recent weeks, according to the Journal, which said officials from the FBI and Department of Health and Human Services’ Office of Inspector General (OIG) participated in some of the interviews.

UnitedHealth Group issued a statement saying it stands behind the integrity of its business in Medicare Advantage, a program in which the federal government hires private insurers to manage care for beneficiaries. Payment rates are increased when insurers submit documentation that enrollees have more health problems, creating a financial incentive to document as many such problems as possible.

“As an important public sector partner serving people’s health needs, we expect and welcome regular reviews of our policies and practices,” UnitedHealth Group’s statement says.

“Independent [federal] audits confirm we are among the most accurate in the industry in our coding practices, demonstrating our commitment to integrity and compliance,” the company said. “Additionally, after more than a decade of a similar Department of Justice challenge to our Medicare Advantage business, the Special Master concluded there was no evidence to support the claims that we were overpaid or engaged in any wrongdoing.”

That special master’s report was issued in March in a long-running whistleblower lawsuit against UnitedHealth Group brought by a former employee in the Twin Cities.

A judge presiding over the case in the U.S. District Court of Central California has scheduled a hearing for Sept. 9 to consider the special master’s recommendation that the whistleblower’s case should be halted.

Auditors with the OIG published a report in 2024 that found UnitedHealth Group stood out from its peers in using questionable diagnosis data to boost Medicare Advantage payments. The company disputed the watchdog group’s findings in the report, which echoed findings from an earlier disputed study.

The stock closed at $302.91, down $4.79, or just under 2%, for the day.

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