Two GOP chairmen on Monday issued subpoenas to several technology vendors as part of an investigation into the security of Hillary Clinton Hillary Diane Rodham ClintonREAD: Cohen testimony alleges Trump knew Stone talked with WikiLeaks about DNC emails County GOP in Minnesota shares image comparing Sanders to Hitler Holder: 'Time to make the Electoral College a vestige of the past' MORE’s private email server.

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Sen. Ron Johnson Ronald (Ron) Harold JohnsonWhite House pleads with Senate GOP on emergency declaration White House, GOP defend Trump emergency declaration GOP senator says Republicans didn't control Senate when they held majority MORE (R-Wis.), the Senate Homeland Security and Governmental Affairs chairman, and Rep. Lamar Smith (R-Texas) the House Science Committee chairman, sent out the subpoenas to three companies.

“The information being sought is a crucial step in bringing greater transparency to Secretary Clinton’s ‘extremely careless’ — I would call it dangerously reckless and grossly negligent — email practices,” said Johnson.

The three companies, which provided software and services to Clinton, have failed to comply with repeated requests for information on Clinton’s private email setup.

The committee is seeking to answer questions about the structure and security of the email system, including whether the cybersecurity measures employed met government standards.

The two chairman made initial requests separately in January and joined forces, merging their efforts into a single investigation, in July.

But the companies — a network security firm, an email services provider and a data backup provider — refused to turn over some information, arguing they did not have Clinton’s consent.

Democrats have already pushed back on the probe.

“I am outraged that the Chairman is recklessly abusing the Committee’s investigatory powers to brazenly do the bidding of the Trump campaign," Science Committee ranking member Eddie Bernice Johnson (D-Texas) said in a statement Monday afternoon. "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."

In February, House Majority Leader Kevin McCarthy (R-Calif.) suggested that the Science Committee probe had overstepped. He told reporters he believed those inquiries should have been under the purview of the House Select Committee on Benghazi, which investigated the attacks on U.S. facilities in the Libyan city.

“I have the same impression as you, that it would be [Rep. Trey Gowdy Harold (Trey) Watson GowdyThe family secret Bruce Ohr told Rod Rosenstein about Russia case Trey Gowdy joins Fox News as a contributor Congress must take the next steps on federal criminal justice reforms MORE's (R-S.C.)] jurisdiction,” McCarthy said at the time, when asked whether Gowdy’s Benghazi panel should be overseeing the investigation. The panel issued its final report in June.

McCarthy also seemed to indicate that Smith hadn’t given the Republican leader a heads-up before sending the letters.

Republicans have hammered Clinton for exposing sensitive information to foreign hackers through her use of the unauthorized server. GOP candidate Donald Trump Donald John TrumpREAD: Cohen testimony alleges Trump knew Stone talked with WikiLeaks about DNC emails Trump urges North Korea to denuclearize ahead of summit Venezuela's Maduro says he fears 'bad' people around Trump MORE has said he hopes Russian hackers accused of breaching the Democratic National Committee (DNC) also got the thousands of emails Clinton deleted from the account.

In his summary of the results of the FBI’s investigation into Clinton’s use of the server — which did not result in charges — Director James Comey said it was “possible” her email was hacked by foreign adversaries.

Hostile actors were able to infiltrate the private commercial email accounts of people with whom Clinton was in regular contact from her personal account, Comey said. He also noted it was well-known that she used a personal domain and that she habitually used her personal email while “in the territory of sophisticated adversaries.”

“I hope the information we will obtain will inform policy changes that can prevent similar misconduct in the future,” Johnson said Monday.

-- Updated 4:49 p.m.