The European Commission will open a four-month, in-depth review of Google'splans to buy rival DoubleClick for $3.1 billion, a source familiar with the situation said on Tuesday.
Google, which stores data on the Internet-surfing habits of consumers, wants to buy DoubleClick to increase its clout in tailoring advertisements to consumer activities.
Both companies are involved in the sale of on-line ads, although their business models differ.
Google has already proposed alterations, and the deadline had been extended to Nov. 13 so the changes could be vetted by customers and competitors.
Google competition counsel Julia Holtz has said that in response to third-party concerns the company had committed to the Commission that it would keep certain DoubleClick business practices unchanged.