WASHINGTON: The Obama administration confirmed for the first time Friday that Hillary Clinton’s home server contained closely guarded government secrets, censoring 22 e-mails that contained material requiring one of the highest levels of classification. The revelation comes three days before the Democratic candidate competes in the Iowa presidential caucuses.

State Department officials also said the agency’s Diplomatic Security and Intelligence and Research bureaus are investigating if any of the information was classified at the time of transmission, going to the heart of Clinton’s defense of her e-mail practices.

The department published its latest batch of e-mails from her time as secretary of state Friday evening.

Republicans have been trying to slow the momentum of Clinton’s campaign by playing up her e-mail issues, saying she played by her own rules when it came to national security.

It’s the potential political costs that are probably of more immediate concern for Clinton. She has struggled in surveys measuring her perceived trustworthiness, and an active federal investigation, especially one buoyed by evidence that top secret material coursed through her account, could negate one of her main selling points for becoming commander in chief: Her national security resume.

The Associated Press learned ahead of the release that seven e-mail chains would be withheld in full for containing “top secret” information. The 37 pages include messages a key intelligence official recently said concerned “special access programs” — highly restricted, classified material that could point to confidential sources or clandestine programs like drone strikes.