Undersecretary of State Victoria Nuland said Tuesday that there are "biological research facilities" in Ukraine the US is concerned Russian forces might seize. She made the comments when asked by Sen. Marco Rubio (R-FL) if Ukraine has chemical or biological weapons.

"Ukraine has biological research facilities which in fact we are quite concerned Russian troops, Russian forces, may be seeking to gain control of, 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," Nuland said.