Material From Russia Investigation Went Missing as Trump Left Office

Material from a binder with highly classified information connected to the investigation into Russian efforts to meddle in the 2016 election disappeared in the final days of Donald J. Trump’s presidency, two people familiar with the matter said.

The disappearance of the material, known as the “Crossfire Hurricane” binder for the name given to the investigation by the F.B.I., vexed national security officials and set off concerns that sensitive information could be inappropriately shared, one of the people said.

The material’s disappearance was reported earlier Friday by CNN. The matter was so concerning to officials that the Senate Intelligence Committee was briefed about it last year, a U.S. official said.

The binder consists of a hodgepodge of materials related to the origins and early stages of the Russia investigation that were collected by Trump administration officials. They included copies of botched F.B.I. applications for national-security surveillance warrants to wiretap a former Trump campaign adviser as well as text messages between two F.B.I. officials involved in the inquiry, Peter Strzok and Lisa Page, expressing animus toward Mr. Trump.

The substance of the material — a redacted version of which has since been made public under the Freedom of Information Act and is posted on the website of the F.B.I. — is not considered particularly sensitive, the official said.

But the raw version in the binder contained details that intelligence agencies believe could reveal secret sources and methods. (The publicly available version contains numerous portions that were whited out as classified.)