The Federal Trade Commission is launching an investigation into Google's proposed purchase of AdMob, a company specializing in ads for small screens.
The US antitrust regulator has requested more information regarding the deal earlier this week, Google's group product manager Paul Feng wrote in a blog post.
Google said it doesn't see any regulatory issues with the proposed deal and remains confident its purchase of AdMob will be approved.
Closer scrutiny has been one consequence of Google's success, added Feng.
The search engine giant said last month that it hoped to buy the Silicon Valley start-up for $750 million in stocks.
AdMob is a network that sells and displays ads to apps and websites viewed from iPhone and other mobile devices. Its profits range from $45 million to $60 million and the FTC hopes to determine if the technology and advertising contacts would give Google an unfair advantage in sales of cellphone ads.
It took months for the FTC to approve Google's earlier purchase of another internet advert company, DoubleClick.