WASHINGTON (AP) — A federal judge says he may order Democratic presidential front-runner Hillary Clinton to testify under oath about whether she used a private email server as secretary of state to evade public records disclosures.

U.S. District Court Judge Emmet G. Sullivan on Wednesday signed an order granting a request from the conservative legal advocacy group Judicial Watch to question six current and former State Department staffers. The list includes some of Clinton’s closest aides from her tenure as the nation’s top diplomat.

Based on what might be gleaned in those interviews, Sullivan says in his order that a sworn deposition from Clinton “may be necessary.”

More than three dozen lawsuits have been filed seeking copies of government records related to Clinton’s service as secretary from 2009 to 2013.