RICHMOND — The U.S. Postal Service on Thursday acknowledged that it inappropriately released sensitive personal information about Democrat Abigail Spanberger, a former CIA officer challenging Rep. Dave Brat (R-Va.), calling it a “human error” that it will address by changing procedures for public information requests.

“The Postal Service deeply regrets our mistake in inappropriately releasing Ms. Spanberger’s Official Personnel File (‘OPF’) to a third-party, which occurred because of human error,” said a statement released by spokesman David Partenheimer.

In the statement, the Postal Service suggested that confidential information involving other people was also mistakenly released.

“We are continuing our review, but believe the issue began in June of 2018, and that only a small number of additional requests for information from personnel files were improperly processed,” the agency said.

Partenheimer said he could not provide further information.

But an aide to Rep. Elijah E. Cummings (Md.), the top Democrat on the House Committee on Oversight and Government Reform, said Postal Service officials who briefed Cummings and Rep. Gerald E. Connolly (D-Va.) on the matter Thursday said the agency mistakenly released personal information about at least three people in addition to Spanberger. Cummings and Connolly have asked the Postal Service’s acting inspector general to investigate.

The admission comes after the Congressional Leadership Fund, a super PAC aligned with House Speaker Paul D. Ryan (R-Wis.), obtained sensitive personal information about Spanberger from a questionnaire she submitted to the federal government while seeking security clearance years earlier. She worked as a postal inspector, a job that also required security clearance, before joining the CIA.

CLF said it obtained a copy of her questionnaire through an ordinary Freedom of Information Act request submitted by America Rising, another political action committee that conducts opposition research on Democratic candidates.

The information released included her Social Security number, medical history and other personal information that the government is prohibited from sharing without the consent of the person whose data has been collected.

Spanberger had suggested that the material might have been illegally leaked by the Trump administration or by foreign hackers, an allegation that a state GOP leader called “reckless” in light of the Postal Service’s admission.

“Spanberger’s sloppy behavior shows that she has far more in common with Barney Fife than James Bond,” said John Findlay, executive director of the Republican Party of Virginia.

The Postal Service requested that America Rising return the sensitive documents. But that did nothing to quell the outrage among former national-security colleagues about the unredacted release of a security-clearance questionnaire, known as an SF86.

More than 200 national-security officials who served under presidents of both parties wrote Thursday to Daniel Coats, director of national intelligence, and Jeff T.H. Pon, director of the Office of Personnel Management.

“[I]t was with surprise, anger, and profound disappointment that we recently learned that our government — whether intentionally or not — violated the trust of one among our ranks,” the letter said.

“It is possible this situation may be the result of a single person’s error,” it continued. “Nevertheless, we note how peculiar it would be for the first victim of such an error to be Ms. Spanberger, who is the Democratic nominee in a competitive U.S. House of Representatives race in Virginia. . . . Absent answers, however, we cannot dismiss the deeply troubling possibility that this was an act of political retribution by this administration in violation of U.S. law.”

In a statement Thursday, Spanberger said that she spoke with the chief postal inspector and that “many unanswered questions remain.” She also said that CLF and America Rising have been circulating her Social Security number and other sensitive information.

“It is my sincere hope that USPS will provide significantly more detail as to how this major failure occurred, and that CLF and America Rising will put decency and country before politics and comply with USPS’s request that they return all documents received,” she said. “I also expect that CLF will comply with our original cease and desist and stop sharing my personal identifying information, including my Social Security Number.”

Spanberger has suggested the release of the personnel file might have been politically motivated given the fact that it was unredacted and the speed with which the Postal Service processed the request: 21 days after America Rising submitted the FOIA request. Spanberger said a firm hired by her campaign to research her background — a standard practice so campaigns know what information is available for rivals to gather — requested her federal employment records in December and is still waiting.

“We take full responsibility for this unfortunate error, and we have taken immediate steps to ensure this will not happen again,” the USPS statement said. “The Postal Service has addressed the issue by providing clear instructions and guidance to our employees tasked with the responsibility for handling these requests, and we will follow up with additional training. The Postal Service also intends to change our process . . . to provide further protection against its inadvertent release, and to ensure that such requests are properly handled.”

Republicans suggested that Spanberger, 39, was raising questions about the release to distract from the fact that the documents showed she once taught English at Islamic Saudi Academy, a Northern Virginia school that critics have dubbed “Terror High” because some students later joined al-Qaeda.

During the 2002-2003 school year, Spanberger worked as a substitute English teacher at the private school, filling in for a teacher who was on maternity leave. She took that job after she’d gotten a conditional job offer from the CIA and was waiting out the long security-clearance process.

She later worked as a covert intelligence officer for the CIA, including time spent overseas trying to disrupt terrorists.

Brat’s campaign has declined to comment on the controversy.

He and Spanberger are engaged in an increasingly competitive race in the 7th District, a formerly solid GOP seat that the Cook Political Report has moved into “toss-up” territory.

Brat won the seat four years ago after pulling off an upset in the GOP primary, snagging the nomination from then-House Majority Leader Eric Cantor. But he faces stiff head winds this year, given President Trump’s unpopularity in the largely suburban district and the fact that some Cantor supporters remain cool to him and that past comments angered some female constituents.