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WASHINGTON — Interior Secretary Ryan Zinke violated his agency’s travel policy by having his wife travel with him in government vehicles, a new report by the Interior Department’s inspector general found.

The report, which has not yet been made public but was posted online Thursday by The Washington Post, also found that Mr. Zinke considered requesting that his wife, Lolita, become an Interior Department volunteer in order to legitimize her travel. Mr. Zinke also had an agency security detail travel with him and his family during a vacation, at a cost to taxpayers of more than $25,000.

In addition, Mr. Zinke asked his security detail to drive a nongovernment employee to the airport on one occasion, also in violation of agency policy, the report found.

The report resulted from one of the at least 18 known federal investigations into allegations of ethical misconduct or other policy violations by Mr. Zinke.