House Oversight Committee Republicans on Tuesday formally called for an immediate hearing on security breaches at the State Department during Hillary Clinton's leadership, after the department said Monday it had uncovered "multiple security incidents" involving more than a dozen employees.

In a letter to Committee Chairman Elijah Cummings, D-Md., ranking committee Republicans Jim Jordan, Mark Meadows and Jody Hice said State Department officials conducting the ongoing security review into the matter should testify.

"We request a hearing to examine widespread security protocol breaches at the State Department concerning former Secretary Hillary Clinton’s private email server," the Republicans wrote. "The unorthodox and unsecure arrangement she maintained exposed classified, national security and diplomatic-sensitive information to a myriad of risks and related issues.

'OMG': TOP HILLARY AIDE STUNNED BY APPARENT EMAIL HACK ATTEMPT IN MIDDLE OF THE NIGHT, FBI DOCS SHOW

"The wide-ranging fallout from these mishandling instances should not be minimized and obscured," they added.

On Monday, the State Department disclosed that it had identified "multiple security incidents" involving current or former employees' handling of Clinton's emails, and that 23 "violations" and seven "infractions" have been issued as part of the department's ongoing investigation.

The information came in a letter to Iowa Republican Sen. Chuck Grassley, who is responsible for overseeing the security review.

"To this point, the department has assessed culpability to 15 individuals, some of whom were culpable in multiple security incidents," Mary Elizabeth Taylor, the State Department's assistant secretary in the Bureau of Legislative Affairs, wrote to Grassley. "DS has issued 23 violations and seven infractions. ... This number will likely change as the review progresses."

President Trump highlighted the finding in a tweet overnight, questioning whether Democrats would investigate and saying, "This is really big."

Former House Oversight Committee Chairman Jason Chaffetz, now a Fox News contributor, said Tuesday that Secretary of State Mike Pompeo should personally handle the probe into departmental misconduct.

"I love Mike Pompeo as the secretary of state," Chaffetz said. "I have the greatest respect for him, he's got his very full plate, but he has to personally get involved with this. Some people should be fired, they should lose their security clearances and they should be in jail."

The State Department, dubbing the matter "serious," said it expected to conclude its investigation by Sept. 1. The department acknowledged that the probe was unusually time-consuming.

"Given the volume of emails provided to the department from former Secretary Clinton's private email server, the department's process has been necessarily more complicated and complex requiring a significant dedication of time and resources," Taylor wrote.

Taylor also noted that disciplinary consequences were pending, and that internal referrals have been made to State Department Human Resources and security officials, even where employees involved no longer work with the department.

Clinton's private email use has remained in the spotlight, as the DOJ looks into potential misconduct in the handling of federal authorities' surveillance and intelligence operations in 2016. Then-FBI Director James Comey said in 2016 that Clinton's handling of classified information was "extremely careless" -- but that "no reasonable prosecutor" would bring charges.

Last month, a trove of partially redacted FBI documents from the agency's investigation into whether Clinton mishandled classified information -- a probe known as the "Midyear Exam" -- revealed that top Clinton aides were shocked at apparent attempts to hack her private email servers.

The document release revealed numerous episodes in which the Clinton team either suspected it had been hacked or seemingly acknowledged that security measures had come up short.

"omg," top Clinton aide Huma Abedin wrote to Justin Cooper, the technology pro overseeing Clinton's private home-based email servers, when he told her shortly after midnight on Jan. 9, 2011, that "someone was trying to hack us."

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And this past March, it was revealed that the Justice Department "negotiated" an agreement with Clinton's legal team that ensured the FBI did not have access to emails on her private servers relating to the Clinton Foundation. Former FBI Agent Peter Strzok testified about the arrangement during a closed-door appearance before the House Judiciary Committee last summer, according to a transcript released this year.

The agreement was reached, Strzok said, because "according to the attorneys, we lacked probable cause to get a search warrant for those servers and projected that either it would take a very long time and/or it would be impossible to get to the point where we could obtain probable cause to get a warrant."

The DOJ's goal, Chaffetz said at the time, was to "make sure they hear no evil, see no evil -- they had no interest in pursuing the truth."