The former Hillary Clinton staffer who oversaw her private email server plans to invoke his Fifth Amendment right not to answer incriminating questions before the House Benghazi Committee, according to a letter his lawyer sent the panel.

The panel on Aug. 11 subpoenaed Bryan Pagliano, the go-to technology fixer for Clinton’s home-made server, to testify privately next Thursday about what he knew of the former secretary of state and 2016 Democratic front-runner's email arrangement. The panel also asked for all his documents about the email arrangement.

But in a letter to the committee, his lawyer said he’d take the Fifth to refuse to answer self-incriminating questions, according to a copy obtained by POLITICO. He also is refusing to turn over documents, citing the ongoing FBI investigation.

“We hope the members of the Select Committee will respect our client’s right to invoke the protections of the Constitution… excuse Mr. Pagliano from personally appearing on September 10, 2015,” reads the letter from attorney Mark MacDougall of Akin Gump Strauss Hauer & Feld LLP.

The Washington Post originally broke the news Wednesday evening. It came just hours before Clinton’s top State Department brass — Cheryl Mills, her former chief of staff, and Jake Sullivan, now her top policy man for the campaign — are set to testify behind closed doors before the panel on Benghazi and the emails scandal.

Pagliano, Clinton’s 2008 campaign IT director who followed her to the State Department, was originally on salary for Clinton’s Senate leadership PAC. He personally helped set up the Clinton email system in the spring of 2009, an arrangement inspired by a home-based server Bill Clinton used in their Chappaqua, New York residence, according to a Washington Post report from last month.

At the State Department, Pagliano continued to manage the server, occasionally being called in to fix it when technology went awry.

In 2013, after Clinton left Foggy Bottom, so did he, for the private sector. The server, now found to have dozens of emails containing classified information and currently in the hands of the FBI, would pass to Platte River Networks, a Denver-based mom-and-pop shop that at one point in time stored some servers in a bathroom closet, according to the Daily Mail.

It is still unclear why or how the Denver company was selected.

Benghazi Committee Democrats wrote their members Wednesday night telling them about the letter, but also assuring them it doesn’t mean something criminal in nature is afoot. Their lead Democrat, Rep. Elijah Cummings of Maryland, blamed Republicans for scaring Pagliano off in a statement issued just after the initial report.

“Although multiple legal experts agree there is no evidence of criminal activity, it is certainly understandable that this witness’ attorneys advised him to assert his Fifth Amendment rights, especially given the onslaught of wild and unsubstantiated accusations by Republican presidential candidates, Members of Congress, and others based on false leaks about the investigation,” Cummings said, referring to the faulty New York Times report that suggested Clinton was under criminal investigation by the FBI for her handling of classified documents. The FBI says it’s simply probing the server set-up and whether documents were at risk — not her personally and nothing criminal in nature.

Cummings continued: “Their insatiable desire to derail Secretary Clinton’s presidential campaign at all costs has real consequences for any serious congressional effort.”

Committee Republicans did not wish to comment on the news, but Benghazi Chairman Trey Gowdy(R-S.C.) has said he has no interest in probing the email controversy that has tormented Clinton on the campaign trail and damaged her standing in the polls.

Senate Judiciary Chairman Chuck Grassley (R-Iowa) and Homeland Security and Government Reform Chairman Ron Johnson (R-Wis.) have instead taken the lead in public, hounding Clinton and her legal team about the server set-up and the safeguards, or lack thereof, of the messages. Both have also reached out to Pagliano for information, according to his lawyer's letter.

But Pagliano’s summons suggests the Benghazi panel is indeed expanding its probe.

Secretary of State John Kerry’s chief of staff Jon Finer is also slated to make an appearance before the panel, potentially even the same day as Pagliano, several sources told POLITICO.

The panel summoned Finer in July before the August recess to testify about State’s apparent difficulty in turning over relevant records to Benghazi investigators — a slow pace that even federal judges have scorned, at least regarding their answers to FOIA requests. But the panel and Finer reached a deal to cancel the hearing after State promised to turn over thousands of pages of new documents.

The fact that the department and the panel are again discussing times for him to come in suggest new problems in document production.

Finer began work at the department, according to a State Department official, in 2013 after the events in Benghazi and is not involved in providing documents to the committee. But he’s increasingly become the target of the committee's frustration since Republicans feel they’re not being heard by the State employees charged with producing the documents to Congress — several of whom worked alongside Clinton’s lawyer David Kendall in years past.

The panel, for example, still does not have all the Mills or Sullivan emails, which it wanted before scheduling their interviews Thursday and Friday.

State says it’s doing everything it can to work speedily.

"The department has made every effort to cooperate with the Benghazi Committee, providing 32 witnesses for interviews and over 70,000 pages of documents, including over 20,000 pages in the last month alone,” said Deputy Spokesperson Mark Toner. "We are continuing to work with the committee on its numerous requests."