The same concerns that led the European Union to block the merger of Deutsche Börse and NYSE Euronext are behind an investigation into Thomson Reuters Corp., said European Union competition commissioner Joaquin Almunia on Thursday.

"If we are to foster growth in Europe, then we need to create optimal conditions for businesses to operate," he said in prepared remarks in Copenhagen. "It is because we wanted to preserve healthy competitive pressure that we prohibited the merger between Deutsche Börse and NYSE a few weeks ago."