In a securities filing, UnitedHealth said it has begun complying with formal criminal and civil requests from the DOJ.

Concerns over alleged abuses of the Medicare Advantage program have sparked several government suits and inquiries in recent years.

UnitedHealth Group, the company that owns healthcare conglomerate UnitedHealth, said on Thursday that it is cooperating with the federal government as it fields criminal and civil requests from authorities.

In a filing with the Securities and Exchange Commission, UnitedHealth said it has "full confidence" in its practices. It added that a court-appointed monitor found no wrongdoing after a decade-long probe into its Medicare Advantage business.

The Minnesota-based provider says in an SEC filing that the investigation is related to UnitedHealth's participation in the Medicare program.

UnitedHealth Group said Thursday it is facing Department of Justice investigations over its Medicare billing practices and is fully cooperating with it.

On Thursday, the giant health care conglomerate announced that it had “proactively reached out” to the Justice Department, after reports of a government investigation had surfaced.

UnitedHealth Group, the parent company of the nation's largest private health insurer, has confirmed it is cooperating with both civil and criminal investigations by the U.S. Depar