U.S. Republican Senator Zachary Nunn has called on the federal government to scrutinize Bitcoin mining hardware manufacturers Bitmain and Cango Inc., saying their growing U.S. operations could pose a national security risk. Nunn noted that Bitmain and Cango "appear to be expanding their U.S. operations through complex ownership structures and financing arrangements that may be inaccessible to regulators and the public." Representatives for both Bitmain and Cango stated that they strictly abide by all U.S. laws and have no ties to any government or state-owned enterprise. Bitmain stated that it was aware of rumors about its planned acquisition of Cango, but that "these rumors are completely untrue." It also denied that it was exploring direct ownership of U.S. power plants and called the claim that its mining rigs could impact infrastructure "unfounded." Cango said it does not comment on "market rumors" or potential mergers and acquisitions. (Bloomberg)