Shares of Google, the No. 1 search engine, fell $4.53 to $624.13 in early Wednesday trading after the European Competition Commissioner said he might bring a complaint against it by March 31.

Google has been probed by the European Commission as well the U.S. Department of Justice and the Federal Trade Commission for alleged abuse of its market share since 2010. Google's share eclipses Yahoo, Microsoft's Bing and others.

I will receive comments from the case team towards the end of the first quarter, said Joaquin Almunia, the European commissioner, in an interview with Reuters.

A probe into practices by the Mountain View, Calif.-based Google could tie up developments for years, much as happened in the past with software giant Microsoft, which had to sign consent decrees to stop bundling its Internet Explorer browser with all new Windows PCs, as well as IBM.

Google, which has a legal staff exceeding 200, has been expecting some kind of litigation. As well, it is also awaiting final clearance from both Washington and Brussels on its $12.5 billion acquisition of Motorola Mobiity, of Libertyville, Ill., to acquire its smartphone business and more than 17,500 patents.

Google's market capitalization is $201.8 billion.