The European Commission is in the early stages of an antitrust investigation into search giant Google, it said on Wednesday.

"The Commission can confirm that it has received three complaints against Google which it is examining," the European Union's top antitrust authority said in a statement.

It added that this doesn't amount to a formal investigation "for the time being."

The Commission informed Google earlier this month, it said, and asked the company to comment on the allegations. It will cooperate closely with the national competition authorities from the 27 E.U. member states, it said.

The complaints filed with the Commission came from U.K. price comparison site Foundem, a French legal search engine called, and a German search site called Ciao that was recently acquired by Microsoft, Google said in a blog posting that appeared overnight European time. The Commission did not name the companies.

Google pointed out in its blog that Foundem is a member of a trade group called iComp, which is largely funded by Microsoft.

Microsoft believes "It’s natural for competition officials to look at online advertising given how important it is to the development of the Internet and the dominance of one player," it said in a statement issued on Wednesday.