(BRUSSELS) - EU antitrust regulators launched on Tuesday an in-depth investigation into Google's takeover of the online advertising firm DoubleClick over concerns the deal could threaten competition.

The European Commission said it would rule by April 2 on whether to allow the deal, which is contested by technology rivals such as Microsoft and Yahoo as well as privacy advocates.

"The Commission's initial market investigation indicated that the proposed merger would raise competition concerns," it said in a statement.

Google ended a bidding war with Microsoft in April by agreeing to pay 3.1 billion dollars (2.1 billion euros) to add DoubleClick to its Internet money-making arsenal.

Although "disappointed" by the Commission's decision, Google chief executive Eric Schmidt said: "We will continue to work with the Commission to demonstrate how our proposed acquisition will benefit publishers, advertisers and consumers."

"We seek to avoid further delays that might put us at a disadvantage in competing fully against Microsoft, Yahoo, AOL and others whose acquisitions in the highly competitive online advertising market have already been approved," he added.

Microsoft has agreed to pay six billion dollars for ad-targeting firm aQuantive and Yahoo paid 680 million dollars to take the reins of Internet ad broker Right Media.

AOL recently bought ad-serving companies ADTECH and TACODA, which specializes in behavioral targeting of online ads.

Yahoo! Europe managing director Ted Coppel welcomed the widely expected decision for an in-depth competition probe into the deal.

"The Commission's decision to open a detailed investigation provides the thorough examination of the proposed merger that Yahoo! believes is needed," he said.

In addition to opposition to the deal from Google's rival's privacy advocates warn its takeover of DoubleClick would give the Internet giant unprecedented access to personal data of web users worldwide.

DoubleClick and Google, along with many other Internet firms, install software bits called "cookies" on people's computers to track when Internet users visit web pages, click on an ads or log into websites.

Companies say this simplifies browsing for users who repeatedly visit certain websites, but it also allows browsing habits to be tracked back to the individual computer or user.

DoubleClick came under fire several years ago from consumer advocacy groups that accused it of using "cookies" without getting permission from the Internet users.

It negotiated a settlement in 2002 that included being more open about what data it keeps while agreeing to purge some of the data it stores within three months of its collection.

Text and Picture Copyright 2007 AFP. All other Copyright 2007 EUbusiness Ltd. All rights reserved. This material is intended solely for personal use. Any other reproduction, publication or redistribution of this material without the written agreement of the copyright owner is strictly forbidden and any breach of copyright will be considered actionable.