Hundreds of billions of dollars have been wiped off the value of Nvidia after the US chipmaker announced an independent investigation would be carried out into its chief executive’s affair with an alleged Chinese spy.The tech firm saw its shares fall by about 4% by close of trade on Monday after Jensen Huang admitted having an extramarital affair.Nvidia’s probe came after reports that the US believed China had targeted the Nvidia boss in an espionage campaign.However, China has rejected the claims, with its foreign ministry saying allegations about Chinese spies were “entirely groundless, speculative and intended to smear and malign China”.Nvidia said it had no reason to believe the company’s secrets or national security were compromised, but a statement by the firm’s board of directors said it would begin an investigation in “light of recent reporting that founder and chief executive Jensen Huang has been the target of a foreign intelligence effort”.US intelligence officials believe Alice Huang, also known as Huang Le, was a spy for Beijing, according to a New York Times report.The report said Secretary of State Marco Rubio sent a memo to top officials in Washington last spring warning that the Nvidia boss was in a close relationship with a Chinese spy.Alice Huang was managing director of Singaporean company Megaspeed, which has had dealings with Nvidia.Jensen Huang admitted he was “unfaithful” to his wife and apologised for hurting her and their children. He added he was “committed to protecting Nvidia and supporting America’s national security” and would cooperate with the investigation.The Nvidia co-founder has also been requested to appear for a joint closed-door briefing for several Congressional committees next week.Members of the US House Foreign Affairs Committee asked Jensen Huang to appear for a closed-door briefing last week on his interactions with Alice Huang and Nvidia’s security protocols around espionage.“Recent reports raise significant national security concerns regarding the PRC’s [China’s] access to sensitive US technology and information,” congressmen Brian Mast, John Moolenaar, and Rick Crawford wrote in a letter.“It is vital that Congress determines the extent to which US national security has been placed at risk.”After Nvidia announced its investigation, other big tech bosses, including Elon Musk, came out in support of Jensen Huang continuing to lead the firm.US President Donald Trump said the Nvidia boss was an “honourable guy”.However, the news sparked a sell-off in Nvidia’s shares, with about $250bn (£190bn) wiped of the company’s market value.