The Commission has carried out unannounced inspections in several member states at companies that distribute “media rights and related rights pertaining to various sports events and/or their broadcasting”.
It comes amid a probe into sports broadcasting rights, but the full details of the investigation are unclear.
Investigators are understood to have seized documents and computer records at the company’s Hammersmith office in west London. They may be returning on Wednesday and Thursday.
FNG is an operating unit of Rupert Murdoch’s 21st Century Fox, which distributes TV and cable channels around the world.
A spokesman for FNG said: “Fox Networks Group (FNG) is cooperating fully with the EC inspection.”
In a statement the Commission said: “The Commission has concerns that the companies involved may have violated EU antitrust rules that prohibit cartels and restrictive business practices.
“Unannounced inspections are a preliminary step into suspected anticompetitive practices. (It) … does not mean that the companies are guilty of anti-competitive behaviour nor does it prejudge the outcome of the investigation itself.”
The Commission did not name any of the companies affected, but Fox Networks Group confirmed the news after it was reported by The Daily Telegraph.
Mr Murdoch’s 21st Century Fox is currently grappling with the Competition and Markets Authority (CMA) after it ruled his planned takeover of the remaining 61% of Sky was not in the public interest.
Fox responded by proposing the sale of Sky News to Disney, also offering to ring-fence funding of the 24-hour news channel.