Members of the House Oversight Committee voted Thursday to hold Hillary Clinton's former IT aide in contempt of Congress over his refusal to comply with a subpoena for documents and testimony.

Bryan Pagliano, the aide who set up Clinton's private email server, failed to appear before the committee on Sept. 13 and declined to provide a copy of the immunity agreement given to him by the Justice Department during the year-long FBI investigation of Clinton's email network.

"Subpoenas are not optional," said Rep. Jason Chaffetz, chairman of the Oversight Committee, at a hearing Thursday to consider Pagliano's fate.

Pagliano worked on Clinton's 2008 campaign before following her to the State Department. Clinton reportedly paid the IT specialist out of her own pocket to operate the private server in her basement through a personal arrangement that was not initially disclosed to the government.

Last year, Pagliano's involvement in the email controversy raised eyebrows when invoked his Fifth Amendment rights and refused to answer questions when called before the House Select Committee on Benghazi. The IT aide has never spoken about the server network in any setting other than his interview with FBI agents.

Three other technology specialists who worked on the email server appeared before the committee last week, but two pleaded their Fifth Amendment rights and walked out of the hearing room.

Rep. Elijah Cummings, the oversight panel's ranking Democrat, noted Chaffetz had issued 12 subpoenas related to the Clinton emails in the past several weeks.

Cummings called the effort to investigate Clinton's conduct an "abuse of authority" given that the committee has not matched it with a probe of Donald Trump's activities. The Maryland Democrat also criticized committee Republicans for sending marshals into Pagliano's workplace to serve him the latest subpoena rather than a staff member.

Rep. Trey Gowdy, R-S.C., compared Pagliano's subpoena to a jury summons, arguing Pagliano should have shown up to the hearing because regular citizens must show up when they are called for jury duty.

"Nobody is going to be prosecuted," Gowdy said of the IT aide's immunity deal. "But I'll bet you that agreement allows for this witness to cooperate with other entities of government."

Democrats on the committee claimed Thursday that Pagliano's legal arrangement with the Justice Department and his past decision to invoke his Fifth Amendment rights should shield him from further testimony.

A second technology specialist, Paul Combetta, also secured an immunity agreement during the FBI investigation of Clinton's server.

Combetta is the focus of congressional scrutiny amid speculation that he asked users of a public online forum for advice on scrubbing Clinton's emails after the Benghazi committee had requested copies.