This official, speaking to The Associated Press on condition of anonymity, said the subpoena was issued by the panel headed by Rep Trey Gowdy.
The official declined to be identified publicly because he wasn't authorised to discuss by name an investigation still in progress.
The panel has "a number of questions" for Blumenthal, the official said, including whether he had any business arrangements that led him to send emails to Clinton and other officials concerning Libya while Clinton was secretary of state. Blumenthal was not an employee of the State Department at the time.
Clinton, who is seeking the Democratic Party's presidential nomination, was in Iowa yesterday for a campaign appearance.
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Rep Elijah Cummings, ranking Democrat on the panel, issued a statement today assailing the committee's GOP leadership for its handling of the subpoena.
"There was no need for the Select Committee to send two US Marshals to the home of Sidney Blumenthal...Especially since the committee never bothered to contact him first to ask him whether he would voluntarily come in," Cummings said.
The State Department said the department has provided 300 emails from Clinton, 19 witnesses and more than 40,000 pages of documents from the initial departmental investigation.
Democrats have complained that Gowdy and other Republicans are drawing out the Benghazi hearings in order to disrupt Clinton's presidential campaign, but Gowdy said that the State Department is to blame for any delays.
Jamal Ware , a spokesman for the Benghazi committee, said yesterday that "questions about why it will take so long and how much it will cost the department to comply with public records requests due to challenges stemming from former Secretary Clinton's personal email arrangement are best directed to State and the former secretary.