The U.S. Justice Department has opened an antitrust investigation of Minnetonka-based UnitedHealth Group, the Wall Street Journal reported Tuesday.

The newspaper cited unnamed sources with knowledge of meetings in recent weeks between investigators and health care industry sources, including physician groups.

Investigators have asked about certain relationships between the company's UnitedHealthcare insurance business — the largest heath insurer in the nation — and its Optum division for health care services, including a fast-growing unit that owns and manages medical groups, the Wall Street Journal reported.

UnitedHealth Group did not comment on the report. The Justice Department also declined to comment.

In February 2022, the Justice Department tried to block UnitedHealth Group's acquisition of Change Healthcare, alleging the merger would harm competition by giving UnitedHealth Group access to rival health insurers' competitively sensitive information.

But a federal judge found the government failed to show during a two-week trial that the acquisition would substantially diminish competition, ruling that UnitedHealth Group's incentives "are not nearly as one-sided as the government suggests."

UnitedHealth completed the $13 billion acquisition in October 2022.