The designation of Durham’s inquiry as a criminal investigation also vastly increases his power to gather information, opening up the possibility of grand jury subpoenas for records and testimony.

The move is sure to please President Donald Trump, who has long complained that he was spied on during the 2016 campaign, despite a lack of evidence to back up that claim. Trump has also accused the Obama administration and FBI officials of treason for their actions in the Russia investigation.

Former officials had expressed repeated concern about Durham’s inquiry in recent weeks, saying there were indications that it was expanding beyond a typical look-back at how high-profile matters were handled. The conversion of the probe to a criminal investigation was first reported on Thursday by the New York Times.

Management reviews are typically conducted by the Justice Department’s Office of Inspector General, which has spent more than a year investigating the contents of Foreign Intelligence Surveillance Act applications that the FBI and Justice Department submitted for Carter Page, an energy industry specialist who had served as a Trump campaign adviser.

Durham’s investigation appears to be broader than the OIG inquiry, although the full scope of his probe remains unclear.

As the impeachment inquiry that is focused on Trump has intensified in recent days, Republicans have been complaining about delays in the release of the OIG report. The Justice Department’s inspector general, Michael Horowitz, said in a letter to lawmakers on Thursday that a draft of his report was still undergoing a classification review process involving department officials and the FBI.

“The process is ongoing and nearing completion,” Horowitz said, without promising any specific timing for public release of the report.

Former officials consulted by POLITICO said that they were puzzled by the development but that it was possible Durham believes someone involved in the Russia probe gave false testimony or intentionally introduced inaccurate information during the Foreign Intelligence Surveillance Act process. The ex-officials said that it was possible the career prosecutor is investigating potential political motivation by officials at the CIA or FBI, but that it would be difficult to pursue as a criminal case.

The chairman of the House Judiciary Committee, Rep. Jerry Nadler (D-N.Y.), and the chairman of the House Intelligence Committee, Rep. Adam Schiff (D-Calif.), voiced concern on Thursday night about the turn of events.

“These reports, if true, raise profound new concerns that the Department of Justice under Attorney General William Barr has lost its independence and become a vehicle for President Trump’s political revenge,” they said in a joint statement. “If the Department of Justice may be used as a tool of political retribution, or to help the President with a political narrative for the next election, the rule of law will suffer new and irreparable damage.”

Andrew Desiderio contributed to this report.