Nvidia receives a subpoena from the US Department of Justice

The antitrust authority had already submitted questionnaires and has now sent legally binding requests to Nvidia, the report said, adding that other companies have also been subpoenaed.

Authorities are concerned that the chipmaker is making it difficult to switch to other suppliers and penalizing buyers who do not exclusively use its artificial intelligence chips, the report said.

The move marks an escalation of the actions the chip giant has faced. Last month, The Information reported that the Justice Department had launched an investigation into the company following complaints from competitors that it may have abused its dominant market position.

The company’s shares fell 2.5% in after-hours trading on Tuesday, after losing 9.5% in the regular session.

Nvidia declined to respond to a Reuters request for comment, while the Justice Department did not immediately respond.