Intelligence Community Inspector General Michael Atkinson, in testimony to House lawmakers about the whistleblower complaint on President Trump's controversial phone call with his Ukrainian counterpart, could not explain what accounted for the 18-day window between the July 25 call and the Aug. 12 complaint filing — or when exactly the whistleblower contacted a key Democrat's staff, sources familiar with the testimony told Fox News.

The whistleblower's contact with Intelligence Committee Chairman Rep. Adam Schiff's staff before filing the complaint in mid-August has prompted renewed scrutiny of Schiff.

The top Democrat previously said “we have not spoken directly to the whistleblower,” but his office later revised the claim, saying that Schiff himself "does not know the identity of the whistleblower, and has not met with or spoken with the whistleblower or their counsel" for any reason.