Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE on Wednesday confirmed that he believes his investigation into Russian election interference was hampered by members of the Trump campaign deleting communications.

"We believe that to be the case,” Mueller said during a hearing before the House Intelligence Committee.

He said he believed the same for the deletion of electronic messages.

ADVERTISEMENT

Asked if it was fair to say “lies, deletion of text messages and witness tampering” left his team unable to fully assess the extent of election interference, Mueller responded “I’m not certain I would adopt that characterization in total."

However, he agreed with his report’s conclusion on potential gaps due to incomplete information, saying “we don’t know what we don’t know.”

The claim was also made in Mueller's final report concluding the Russia investigation, which read in part: "The Office learned that some of the individuals we interviewed or whose conduct we investigated—including some associated with the Trump Campaign—deleted relevant communications or communicated during the relevant period using applications that feature encryption or that do not provide for long-term retention of data or communications records."

Rep. Eric Swalwell Eric Michael SwalwellSwalwell calls for creation of presidential crimes commission to investigate Trump when he leaves office 'This already exists': Democrats seize on potential Trump executive order on preexisting conditions Swalwell: Barr has taken Michael Cohen's job as Trump's fixer MORE (D-Calif.), who briefly ran for the 2020 Democratic presidential nomination, further asked Mueller on Wednesday why truthful statements were important to such investigations.

"Because the testimony of the witness goes to the heart of just about any criminal case you have," Mueller replied.