Then-Secretary of State Hillary Clinton checks her mobile phone at a U.N. Security Council meeting in 2012. (Photo: Richard Drew/AP)

The former aide to Hillary Clinton who helped set up and maintain her private email server has declined to talk to the FBI and the State Department inspector general’s office, as well as a congressional committee, invoking his Fifth Amendment right not to incriminate himself, sources familiar with the investigation confirmed to Yahoo News.

The move by Bryan Pagliano, who served on Clinton’s 2008 campaign and later as a technology officer in the State Department, to decline to cooperate in two federal probes considerably raises the stakes in the Clinton email investigation, the sources said. It confronts the Justice Department with a decision about whether to grant him immunity in exchange for his testimony — a move that could be taken only were the department to escalate the probe into a full-scale criminal investigation, the sources said.

Pagliano’s decision this week to decline to testify before a congressional committee investigating the death of the U.S. ambassador in Benghazi was first reported Wednesday night by the Washington Post. But Pagliano’s earlier rebuffs to federal investigators, including the FBI, have not been previously reported.

Pagliano, who maintained the private email server in the basement of Bill and Hillary Clinton’s home in Chappaqua, N.Y., was first contacted by the State Department inspector general’s office in June, the sources said. The inspector general was at that point in the early stages of its investigation into Clinton’s use of a private email server to conduct official business.

But Pagliano — a potential key figure in the probe — declined to speak to the inspector general’s investigators, informing them through his Washington lawyer, Mark MacDougall, that he would invoke his Fifth Amendment right, the sources said.

Then, in late July, the State Department inspector general and the inspector general for the director of national intelligence referred the matter to the FBI counterintelligence division to determine if classified information was mishandled through the use of the private email server after finding evidence that classified information was communicated on emails sent through the server. But officials stressed at that time that the inquiry was an intelligence probe and not a criminal investigation.

Story continues

At that point, the FBI also sought to question Pagliano and he again refused. His refusal to answer questions was communicated by his lawyer to senior lawyers in the counterintelligence section of the Justice Department’s national security division — one of whom had previously been in charge of the investigation into former CIA Director David Petraeus, the sources said.

MacDougall, Pagliano’s lawyer, declined any comment, and sources note that is not uncommon for lawyers with clients in sensitive investigations to invoke their Fifth Amendment right against self-incrimination. Even if their clients are not the targets of the investigation, lawyers argue that the clients could be confronted with documents or questions they are not prepared for and inadvertently subject themselves to charges that they are not being truthful.

But sources familiar with the Clinton probe said Pagliano is a potentially central figure who may be one of the few who can answer key questions about why the private email server was set up, what he was told by Clinton about its purpose, who had access to it and what protections existed to guard against hackers or any other outside intrusions.

Pagliano had served as information technology director for Clinton’s 2008 campaign. He later moved to the State Department office of the chief technology officer but continued to maintain access to the private server “remotely” as well as paying occasional visits to the Clintons’ home to help maintain it, the sources said.

On Aug. 11, the special committee investigating Benghazi, which first uncovered Clinton’s use of a private email address and server, subpoenaed Pagliano to turn over documents and testify at a hearing on Sept. 10. But this week, MacDougall wrote its chairman, Rep. Trey Gowdy, R-S.C., a letter informing him that his client would not answer questions, citing the fact that the issue “is a subject of investigative activity by the Federal Bureau of Investigation and the Department of Justice.”

“While we understand that Mr. Pagliano’s response to this subpoena may be controversial in the current political environment, we hope that the members of the Select Committee will respect our client’s right to invoke the protections of the Constitution,” MacDougall and two other lawyers working with him wrote.

Asked about the matter at a press stakeout today, Gowdy said he understood why clients invoke the Fifth Amendment, “but you’ll have to ask him why he did. And you’re free to glean whatever inference you want from the fact that he did it.”

In a statement today, a Clinton campaign spokesman said the former secretary has urged Pagliano to cooperate in the probe.

“We have been confident from the beginning that Hillary Clinton’s use of a personal email was allowed and that she did not send or receive anything marked classified, facts confirmed by the State Department and the Inspector General,” said campaign spokesman Nick Merrill in a statement.

“She has made every effort to answer questions and be as helpful as possible, and has encouraged her aides, current and former, to do the same, including Bryan Pagliano,” Merrill added.

He also noted that two of Clinton’s former aides, including former chief of staff Cheryl Mills, are due to testify in closed sessions before the Benghazi committee this week. Mills’ session is scheduled for today.

House Select Committee on Benghazi Chairman Trey Gowdy. (Photo: Susan Walsh/AP)