U.S. Department of Justice is carrying out a criminal investigation into UnitedHealth Group

The U.S. Department of Justice is carrying out a criminal investigation into UnitedHealth Group (NYSE: UNH) for possible Medicare fraud, the Wall Street Journal reported on Wednesday.

UnitedHealth said it had not been notified by the DOJ about the “supposed criminal investigation reported,” and the company stood by “the integrity of our Medicare Advantage program.” The stock fell 8% in after-hours trade following the report.

The health insurer has been under pressure for months. On Tuesday, UnitedHealth Group’s CEO, Andrew Witty, stepped down unexpectedly, and the company simultaneously suspended its 2025 financial forecast due to rising medical costs. The announcement sent shares plunging nearly 18% to a four-year low.

Stephen Hemsley, who led the company for more than a decade until 2017, is taking back the reins following setbacks including the December murder of Brian Thompson, the CEO of its insurance unit, which catapulted UnitedHealth into the public consciousness.

The DOJ’s healthcare-fraud unit is overseeing the criminal investigation, which focuses on the company’s Medicare Advantage business practices, the Journal reported, citing people familiar with the matter.

While the exact nature of the potential criminal allegations against UnitedHealth is unclear, it has been an active probe since at least last summer, the newspaper said.

A DOJ spokesperson declined to comment to the Journal about the fresh criminal probe. The department did not immediately respond to Reuters requests for comments.