House Republicans served subpoenas Monday to three technology companies that handled Hillary Clinton's private emails in search of documents needed for their investigation of her private server network.

The Science, Space and Technology Committee ordered Austin McChord, CEO of Datto, Inc., to produce to the committee by Sept. 9 documents related to his firm's involvement with the maintenance of the Clinton email server.

Two other technology company CEOs, Treve Suazo of Platte River Networks and Victor Nappe of SENCAP Network Security Corporation, also received subpoenas from the committee to produce documents.

Cover letters included with the subpoenas noted that the committee had sought the "voluntary cooperation" of the firms for several months before serving the executives.

The subpoenas came weeks after the FBI determined Clinton and her aides were "extremely careless" in their handling of the more than 100 classified emails that passed through the private network. Employees at tech firms hired to handle the emails may have inadvertently had access to classified material.

Rep. Eddie Bernice Johnson, the committee's ranking Democrat, blasted Republicans for serving the subpoena Monday.

"I am outraged that the chairman is recklessly abusing the committee's investigatory powers to brazenly do the bidding of the Trump campaign," Johnson said. "I am certain that the Science Committee will not uncover any 'smoking gun' after this issue has already been thoroughly investigated by the Benghazi Committee at a cost of $7 million in taxpayer dollars, as well as by the FBI."

Sen. Ron Johnson, chairman of the Senate Homeland Security Committee, cosigned the subpoenas. He praised the House Science Committee for pursuing documents from the tech companies.

"I strongly support Chairman [Lamar] Smith's decision to subpoena the three companies, which is why I co-signed the cover letter accompanying each subpoena," Johnson said. "The companies have direct and unique knowledge of [Clinton's] private server and email account."