The Pentagon's inspector general announced on Wednesday it has launched an official investigation into whether acting Defense Secretary Patrick Shanahan has violated ethics rules by favoring his former employer Boeing.

The backdrop: The independent watchdog group Citizens for Responsibility and Ethics filed an ethics complaint on March 13 alleging that Shanahan had unfairly promoted Boeing — a company he worked at for 31 years — and disparaged direct competitors like Lockheed Martin.

Politico reported in January that Shanahan had spoken negatively about Lockheed during a meeting at the Pentagon, while Bloomberg reported in December that Shanahan pushed the Air Force to contract Boeing for F-15X fighter planes. Shanahan was supposed to recuse himself from any decisions related to Boeing when he was confirmed by the Senate.

Shanahan has denied the claims, but told a Senate committee last week that he supports the investigation.