The Justice Department has granted immunity to a former State Department staffer who worked on Hillary Clinton’s private email server, Fox News has confirmed.

The Washington Post, quoting a senior law enforcement official, first reported that the FBI secured the cooperation of Bryan Pagliano, who worked on Clinton’s 2008 presidential campaign before setting up the private server at her New York home in 2009.

Current and former agents told the newspaper that agents will likely want to interview Clinton and her senior aides about the decision to use a private server, and whether any of the participants knew they were sending classified information in emails as part of the ongoing investigation.

Republican presidential candidate Sen. Ted Cruz of Texas called the latest developments on the Clinton investigation "ominous" in an interview with Fox News' Megyn Kelly on "The Kelly File," and that it meant the process was moving to "a whole other level."

"That suggests the legal jeopardy is getting greater and greater," he said Wednesday.

Attorney General Loretta Lynch said Monday in an interview with Fox News that the Justice Department has no deadline for concluding the Clinton email investigation and that it’s being handled “like any other review,” even with the presidential election just months away.

Lynch said on "Special Report with Bret Baier" that the investigation is being handled by the agency’s “career independent lawyers” and that they will “review the facts and the evidence and make a determination in due course.”

Lynch, nominated by President Obama to the attorney general post in 2014, also said the agency would look “efficiently, fairly, thoroughly, without any kind of artificial deadline” into whether Clinton broke any laws as secretary of state by using a private email server for official communications.

Lynch was steadfast in declining to discuss specifics about the Clinton case -- including whether Clinton has been interviewed, if a grand jury had been convened, which departments within the agency are involved and whether she would ultimately decide whether the case will go forward.

“We handle it in the same way, and that's what I'd like to convey to the American people,” she said. “We owe it to the citizens and we owe it to anybody who may be involved in the matter.”

She also declined to comment on Clinton's then-chief of staff Cheryl Mills maintaining her top secret security clearance despite sending information that's now being classified to the Clinton Foundation.

Click for more from The Washington Post

Fox News' Catherine Herridge contributed to this report.