The U.S. Federal Trade Commission is preparing to serve subpoenas to Google as a first step in a broad antitrust investigation of the search engine and advertising giant, according to a report in the Wall Street Journal.The probe would focus on whether Google is using its search engine to unfairly drive traffic to its growing group of Web properties, said the Journal article, citing unnamed sources.Representatives of Google and the FTC declined to comment on the report. The information "didn't come from us," said an FTC spokeswoman.The European Commission opened its own antitrust investigation into Google in November. The European investigation focused on allegations that Google abused its dominant position in online search to promote its other services, such as price comparison.Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's e-mail address is email@example.com.