"Undersecretary of State for Political Affairs Victoria Nuland previously said at a hearing in Congress that the US has "biological research facilities" in Ukraine and she said "we are now in fact quite concerned that Russian troops… may be seeking to gain control of [those labs], so we are working with the Ukrainians on how they can prevent any of those research materials from falling into the hands of Russian forces should they approach."
Ukraine has 26 of these biolabs, all of them funded by the Pentagon. Ukraine is the poorest country in Europe, and isn't exactly a hotbed for scientific research, so you've got to wonder why there are so many of these supposedly harmless biolabs.