European Union Antitrust Commissioner Joaquin Almunia

European Union Antitrust Commissioner Joaquin Almunia

Giuseppe Aresu/Bloomberg

Joaquin Almunia, the region’s antitrust chief, said a complaint about Google filed by Microsoft Corp. last week “would not be the last one” and regulators had received more than 500 responses to questionnaires sent to Web companies, publishers, and advertisers earlier this year.