The US Federal Trade Commission has opened an in-depth probe into Nvidia's agreement to acquire Arm Ltd, Bloomberg reported on Friday, citing a source.
The FTC has sent information demands to third parties, according to Bloomberg.
The FTC and Nvidia did not respond to requests for comment outside regular working hours.
Nvidia struck a deal with Japan's SoftBank Group in September to buy UK-based chip designer Arm Holdings for as much as $40 billion.
In addition to the FTC probe, Alphabet Inc, Qualcomm Inc and Microsoft Corp have complained to U.S. antitrust regulators about the deal, the report added, citing people familiar with the process.
Arm Holdings supplies intellectual property to Apple, Qualcomm and a host of others for chips that power nearly all of the world's smartphones.
Earlier in January, Britain's Competition and Markets Authority said it would start an investigation into Nvidia's deal to buy Arm.
(Reporting by Tiyashi Datta and Kanishka Singh in Bengaluru; Editing by Anil D'Silva and Leslie Adler)