Richard Blumenthal actually said...

We plan to continue to hold NTSB accountable for delivering on this responsibility.

Not in the least because they have spent $6 million to hire Cambridge Analytica as a consultant, as an agent, in that capacity.

There is a series of circumstantial evidence. No conclusion reached yet, but certainly a basis to investigate.

But if it doesn't pass the smell test and it's worthy of investigation, the special counsel, Robert Mueller, will look into it.