Numerous foreign companies settled in the region, some of which also produce for export.
Abbott Laboratories and Boston Scientific, which also produce the stents, have said previously that they have been contacted by investigators.
Experts say the small, unregulated factories could pose dangers because they do not have the same controls and rules as large slaughterhouses, which also produce crude heparin.
The scientists believe that the calls may have evolved in a group of reptiles that preceded modern crocodiles and birds, which also produce pre-hatching calls.
Katanga's mines, which also produce cobalt, are located in the copper belt within the Democratic Republic of Congo (DRC), a country that has been ravaged by civil war and corruption.
Li Xiaodong creates a labyrinth of twig screens that leads sometimes to claustrophobic dead-ends, but also to an unexpected inner courtyard, amplified by mirrors, which also produce an uneasy self-consciousness of your own presence in the space.
