UnitedHealth Group disclosed in a July 23 regulatory filing that the U.S. Department of Justice has opened both criminal and civil investigations into aspects of the company’s Medicare Advantage billing practices. The insurer said it had proactively contacted the department after media reports surfaced and is now complying with formal requests for information. The Minnetonka, Minnesota-based company stated it has “full confidence” in its practices. It cited independent audits by the Centers for Medicare & Medicaid Services that it says confirm the accuracy of its risk-adjustment coding, as well as a court-appointed Special Master who found no evidence of wrongdoing after a decade-long civil challenge. UnitedHealth has also commissioned an outside review of its coding and pharmacy operations. Investors reacted swiftly: the stock fell as much as 5% in pre-market trading to about $283.50, dragging Dow futures lower even as other benchmarks held steady. UnitedHealth shares have already shed almost half their value this year amid rising medical costs and leadership upheaval.