Google has confirmed that the US Federal Trade Commission is investigating its proposed $3.1bn (£1.65m) purchase of online advertising seller DoubleClick.
Google, in a statement, said it is confident the FTC will approve the deal.
Google issued the statement after press reports that the FTC started an investigation into the deal last week. The investigation comes after privacy groups filed a complaint with the FTC.
An FTC spokesman declined to comment on the investigation, instead referring to the Google statement. The FTC will have no more immediate comments on the investigation, the spokesman said.
Google announced the deal last month. Microsoft had also pursued DoubleClick, which places online advertising for more than 1,500 clients.
On April 20, the Electronic Privacy Information Centre, the Centre for Digital Democracy, and the US Public Interest Research Group, filed a complaint with the FTC, asking the agency to block the merger unless it obtained guarantees from Google and DoubleClick that they will protect Internet users' privacy.
The groups want a guarantee that Google will destroy all cookies and other persistent identifiers resulting from Internet searches that could be personally identifiable.