Since people seem incredulous that the FBI would talk to a witness more than once, here's a data point: I, personally, have sat through multiple 12-hour FBI interviews with a witness who was not only formally cleared, but given immunity for the testimony. I'm sure if busybodies were watching who walked into the office over those weeks, they would have posted about this completely innocent person's guilt. But it was just someone who happened to know a lot about the subject matter and the company. So unless LE comes out and names someone a POI or a suspect, they could just be a helpful witness.