science. their plea comes, as the u.s. is ramping up its own efforts to flush out two theories including a possible-lab leak, in china. cnn's david culver has reported extensively from wuhan, where the virus was first identified. and he filed this report from shanghai. >> reporter: president biden, ordering u.s. intelligence to dig deeper into the origin of covid-19. putting renewed focus on the chinese city where it was, first, publicly detected, wuhan. the white house says there are two-possible origin theories. the first? a natural spread from animals to humans, possibly amplified inside this once-crowded wuhan seafood market. the second and far-more controversial possibility? a leak of the deadly virus from this wuhan lab. >> we know that china engaged a massive coverup, starting from day one, involve -- including destroying samples, hiding records, imprisoning people asking -- in china asking basic questions and placing a gag