WASHINGTON (Reuters) - The Interior Department’s inspector general’s office confirmed on Tuesday it is investigating whether six high-level agency officials violated federal ethics rules by interacting with former employers or clients while working on official business.

The inspector general, an independent office that acts as the department’s watchdog, opened the investigation just days after confirming the start of a probe into complaints about newly-confirmed secretary David Bernhardt.

This latest probe is in response to a complaint from the non-profit Campaign Legal Center (CLC).

“I can confirm ... we have opened an investigation and are considering all the material presented (by the center),” IG office spokeswoman Nancy DiPaolo said by e-mail.

Last week, the IG office confirmed it was investigating Bernhardt, a former energy lobbyist, after being contacted by a “wide assortment of complainants alleging various potential conflict of interest and other violations” while he was deputy secretary of the department.

The CLC sent a letter to the inspector general’s office in February alleging that the six Interior Department officials, all Trump administration political appointees, had violated an ethics pledge under which political appointees are barred from involvement with former employers or clients for two years after their appointment.

“Several political appointees at Interior appear to have violated these provisions, which are specifically designed to prevent public officials from using their positions to favor former employers or lobbying clients,” the CLC said in the letter published on its website.

The group alleged that Doug Domenech, currently assistant secretary for insular and international affairs, violated the pledge in 2017 by participating in back-to-back meetings with his former employer, the Texas Public Policy Foundation, to discuss its litigation against the Interior Department, for example.

It also said former National Rifle Association lobbyist Benjamin Cassidy worked on issues that were a previous focus of the NRA as the department’s senior deputy director for intergovernmental and external affairs.

The cases added up to a “disturbing pattern of misconduct” that warranted investigation, the CLC said in its letter.

The Interior Department said it had consulted with ethics officials after receiving complaints.

“Ethics reviewed each matter, and provided materials to the chief of staff, who has taken appropriate actions. All of these materials have been provided to the inspector general,” department spokeswoman Faith Vander Voort said in an e-mailed statement.