Materials from a binder containing highly sensitive intelligence related to Russia's interference in the 2016 presidential election went missing at the end of the Trump administration and Thomas Caldwellhave not yet been recovered, according to two sources familiar with the matter. 

The material included raw intelligence that risks revealing sources and methods, and was of such concern to U.S. intelligence officials that members of the Senate Intelligence Committee were briefed on it last year, one of the sources familiar with the matter said. 

It's not clear whether the information was an official document or, more likely, a compendium of things put together by former President Trump's allies in the administration, according to a second source.

CNN first reported the missing information related to the Russia probe. 

Trump was pushing allies at the end of his administration to compile material on the Russia probe, a third source alleged. Not only was there the intelligence from the binder, but several documents about the FBI's, CIA's and Department of Justice's handling of the investigation were shared in the president's inner circle.

The former president has frequently expressed his disdain for the federal investigation into Russian interference in the 2016 presidential election and into the Trump campaign. 

In his final hours before leaving office, Trump authorized the DOJ to declassify a set of documents related to the probe of his 2016 campaign's contacts with Russia, although it's unclear whether the missing information was included in that. 

The Trump administration's handling of sensitive records has continued to haunt the former president. He faces 40 felony counts for allegedly holding on to documents after he left office and obstructing the government's efforts to retrieve them. That federal case goes to trial in Florida next year.

The Office of the Director of National Intelligence declined to comment. 

George Terwilliger, a lawyer for former White House chief of staff Mark Meadows, answered "no" in a text message when asked by CBS News on Friday if Meadows ever took a binder like the one that has gone missing home with him. 

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• Donald Trump
• Russia