Is the US FBI a credible investigator for something like this?

a) I don't know that they have the right skills to track down patient zero of a disease.

b) They certainly don't have jurisdiction to do such an investigation in a foreign country, unless invited, and there's no way they were invited.

I strongly doubt we'll ever see a good answer on this, unless we get very lucky and some random research sample is looked at later that shows detection months earlier in a different location or if the Chinese did a good investigation and kept it quiet, but it leaks in a couple decades.

A timely and thorough investigation might have been able to determine an origin, but the US FBI certainly didn't do one.

I don’t but this guy in your article does

> A natural origin is still the more likely theory, said Professor David Robertson, head of viral genomics and bioinformatics at University of Glasgow.

Your link also says

>> And other US government agencies have drawn differing conclusions to the FBI's.

They don’t disagree. They don’t know. They just said what’s most likely. They don’t even give a %