Federal investigators’ decision to search the Maryland home of the former national security adviser, John Bolton, was partly influenced by a foreign hack of his personal email account years ago, according to a heavily redacted search warrant affidavit released Friday.

The document, unsealed after a legal challenge from news organizations, suggests that intelligence related to the hack provided investigators with probable cause to believe that classified records and national defense information were being illegally stored at Mr. Bolton’s residence following his departure from the Trump administration in 2019.

Mr. Bolton, a longtime foreign policy hawk who served for 17 months in President Trump’s first administration, has not been charged with a crime.

While more than a dozen pages of the affidavit are partially or fully redacted, a section headline reads, “Hack of Bolton AOL Account by Foreign Entity.” A source familiar with the investigation told CNN that the American intelligence community believes Mr. Bolton’s emails showed signs of being intercepted by China, Russia, or Iran, with Iran considered the top suspect.

The affidavit also details interactions between Mr. Bolton and a senior National Security Council official, Ellen Knight, who reviewed the manuscript for his 2020 book, “The Room Where It Happened.” Ms. Knight reportedly found “significant amounts” of classified information, some at the top-secret level, and noted that Mr. Bolton “appeared to acknowledge” the need to remove it. These discussions appear to be a core part of the investigation before a federal grand jury.

In a statement last week, Mr. Bolton’s attorney, Abbe Lowell, maintained his client’s innocence, stating the records found were “ordinary” and that “nothing inappropriate was stored or kept by Ambassador Bolton.”

Mr. Lowell added on Friday, “the materials taken included documents that had previously been approved as part of a pre-publication review for Ambassador Bolton’s book and are the kinds of records that would be kept by a 40-year career serving at the State Department, as an Assistant Attorney General, the US Ambassador to the United Nations, and National Security Advisor.”

The FBI seized phones, computers, hard drives, and documents during the August search of Mr. Bolton’s home and a separate search of his office in Washington, D.C.

In releasing the redacted affidavit, U.S. Magistrate Judge Timothy Sullivan said that revealing more could jeopardize the ongoing criminal investigation. “The investigation involves matters of national security and highly classified materials to which the public has no right of access,” the judge said.