Two US senators have asked the Federal Trade Commission (FTC) to launch a formal anti-trust investigation into Google.
Senators Herb Kohl and Mike Lee have written to the FTC (PDF) about their fears that Google could be abusing its dominant position in the market, or could do so in the future.
Kohl and Lee completed an investigation into Google, via a subcommittee, in September. The senators admitted that they found no evidence of wrongdoing, but said that the matter requires a proper investigation.
"While we take no position on the ultimate legality of Google's practices under the anti-trust laws and the FTC Act, we believe these concerns warrant a thorough investigation by the FTC," they said.
The senators added that a key question for the FTC is whether Google favours its own online properties when serving search results, and suggested that Google's own executives had admitted as much during the subcommittee hearings.
Kohl and Lee have also asked the FTC to consider what Google could do with Android, warning that the firm could force hardware manufacturers that use the operating system to set its search engine as the default.