Inc’s US$4 billion investment into artificial intelligence firm Anthropic is facing the prospect of an in-depth U.K. antitrust probe, a week after the agency warned of Big Tech’s “interconnected web” of deals into the booming market.

The Competition and Markets Authority said Wednesday it was gathering information from market players to determine whether the collaboration between the two firms threatens competition in the U.K.

It also said it was looking at Microsoft Corp.’s partnership with Mistral and Inflection AI, a start up that lost its chief executive and most of its staff to Microsoft last month.

“We will assess, objectively and impartially, whether each of these three deals fall within U.K. merger rules and, if they do, whether they have any impact on competition in the U.K.,” said Joel Bamford, executive director of mergers at the CMA.

The swift action follows findings from the agency that the pattern of large tech firms investing in AI startups could allow them to shape the markets and cause competition concerns. It said it wanted to learn from the past, where a winner-takes-all dynamic led to the rise of a small number of all-powerful platforms.

“We remain confident that common business practices such as the hiring of talent or making a fractional investment in an AI start up promote competition and are not the same as a merger,” a Microsoft spokesperson said.

Microsoft’s partnership with OpenAI Inc. is already in the midst of an initial investigation by the agency which announced it was looking into it in August.

That tie-up is set to avoid European scrutiny with regulators not seeing the need for a formal investigation as its falls short of the definition of a takeover.

The U.S. Federal Trade Commission is also at the initial stages of examining the nature of Microsoft’s investment in OpenAI and whether it may violate antitrust laws.

“It’s unprecedented for the CMA to review a collaboration of this type,” Amazon said in a statement. “Our collaboration with Anthropic includes a limited investment, doesn’t give Amazon a board director or observer role, and continues to have Anthropic running its models on multiple cloud providers.”

Anthropic, Mistral and Inflection didn’t immediately respond to requests for comment.