Nvidia has been subpoenaed by the Department of Justice in an antitrust investigation

One week after reporting another record quarterchipmaker Nvidia NVDA was subpoenaed by the US Department of Justice complaints that they violate antitrust laws.

The Justice Department also subpoenaed other companies for evidence after initially sending out questionnaires about Nvidia’s business practices, Bloomberg reported, citing unnamed people familiar with the matter.

In June, the Department of Justice and the Federal Trade Commission reached an agreement to conduct antitrust investigations in Nvidia and fellow AI industry leaders Microsoft and OpenAI.

US officials are concerned about complaints that include how Nvidia has made it difficult for customers to switch chip suppliers. Nvidia and the Justice Department declined to comment.

The Justice Department reached out to the chipmaker’s competitors, including Advanced Micro Devices and AI chip startups, to gather information, including allegations of threatening customers which buys products from competitors, as well as Nvidia’s recent acquisitions of AI software startups, The Information reported in August, citing unnamed people familiar with the matter. Some of Nvidia’s customers fear it will charge a higher price for its chips or even restrict the number of chips it sells if a customer also buys chips from competitors, customer employees told The Information. Justice Department officials were investigating whether the chipmaker pressured some of its customers, including cloud providers that lease servers powered by Nvidia chips to developers, to buy more of the company’s technology.

Meanwhile, Nvidia’s stocks took hits since its second quarter earnings report. Shares of the chip maker fell about 9.5 percent at the close on Tuesday, losing a record $279 billion. Its shares fell about 2 percent in after-hours trading. However, Nvidia shares are up about 124.2% so far this year.