A federal grand jury has been presented with evidence as part of a probe into whether former Interior secretary Ryan Zinke lied to federal investigators about his involvement in blocking two American Indian tribes from opening a casino, the Washington Post reports, citing anonymous sources.

The Interior Department's inspector general's office has been investigating whether Zinke was improperly swayed by lobbying and political pressure since last year, following POLITICO's reporting on the efforts of MGM Resorts International and Nevada Republicans to stave off competition from the tribes. The state of Connecticut and the Mashantucket Pequot and Mohegan tribes also are suing over Interior's 2017 decision to block the two tribes from opening a casino.

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Citing "two individuals briefed on the matter," the Post reported today that prosecutors are presenting evidence related to the casino probe to a grand jury in Washington. The Justice Department did not immediately respond to a request for comment. A spokesman for the U.S. Attorney's Office in Washington declined to comment.

Interior spokeswoman Faith Vander Voort told POLITICO, "The Department cannot comment on matters in litigation or investigation."

Zinke declined to comment. "Have a great day, bye-bye," he said when reached by a reporter on his cell phone this afternoon, before hanging up.