NVIDIA chief executive officer Jensen Huang’s wealth tumbled the most ever after a rout in chip stocks and a report that the US Justice Department (DOJ) sent the tech firm subpoenas as part of an escalating antitrust probe.

Huang’s net worth slumped about US$10 billion to US$94.9 billion on Tuesday (Sep 3), the biggest single-day US dollar drop for him since the Bloomberg Billionaires Index began tracking his wealth in 2016. The plunge followed a 9.5 per cent drop in the shares of the chipmaker he co-founded. A spokesperson for Nvidia declined to comment.

The success of Nvidia’s products – along with struggles by rivals to field alternative chips – made the firm a crucial part of the supply chain for some of the biggest companies in the world. The DOJ is now sending legally binding requests that oblige recipients to provide information, according to a Bloomberg News report citing sources familiar with the investigation. This makes the government a step closer to launching a formal complaint.

Antitrust officials are concerned that Nvidia is making it harder to switch to other suppliers and penalises buyers that do not exclusively use its artificial intelligence chips, according to the sources.

Huang is the world’s 18th richest person and his wealth has grown by US$51 billion year-to-date, even after the sharp drop on Tuesday, according to the index.

He was raised in Taiwan and Thailand before emigrating to the US, where he co-founded what became now the world’s third-biggest firm by market value in 1993.