A classified binder containing highly sensitive intelligence on Russian election interference went missing during former President Donald Trump’s last days in office, CNN reports. This raised alarms in the intelligence community that critical national security secrets could be exposed.

“Its disappearance…was so concerning that intelligence officials briefed Senate Intelligence Committee leaders last year,” the CNN report states.

The raw intelligence apparently informed assessments that Russian President Vladimir Putin had worked to assist Trump’s 2016 campaign. Access was restricted to only certain officials at CIA headquarters given its sensitivity.

The binder was last seen at the White House while Trump aimed to declassify documents tied to the Russia probe, under then-chief of staff Mark Meadows’ control. An unredacted version disappeared amid the final, chaotic hours of the administration, with circumstances still unclear.

“One theory has emerged about the binder’s whereabouts,” CNN reports. “Cassidy Hutchinson, one of Meadows’ top aides, testified…she believes Meadows took home an unredacted version.”

Meadows’ attorney strongly denies mishandling classified information, calling any such suggestion “flat wrong.” The mystery continues of where this confidential binder ended up.