Google may be the subject of as many as nine antirust complaints investigated by the European Commission, if sources close to Reuters can be believed.

The search giant is already under investigation in four cases by the Commission but according to sources, it will be hit with new complaints by small companies, including three cases from national regulators and two coming as fresh complaints:

The two sources, which remain anonymous due to the sensitivity of the matter, said:

“The Commission has nine formal complaints now. The new complaints come from small companies.”

Google is already answering questions related to its handling of content and data of its rivals, most notably Microsoft. Microsoft stated that Google had “engaged in a broadening pattern of walling off access to content and data that competitors need to provide search results to consumers and to attract advertisers.”

It has also been in talks with the European Commission earlier the investigation, which began in November 2010 with complaints from three European vertical search engines before expanding to cover news and mapping practices following additional complaints in December. The formal arrival of Microsoft on the scene may well throw out any hope Google had of a swift end to the probe.