Yahoo is now officially using of Microsoft's search engine, Bing, for its back-end search results, Bing said today. According to Bing, it is now powering Yahoo's search results in the US and Canada, in English. The two had announced in July that they had begun testing the transition of Yahoo to use Bing. Bing said that it will be supporting other language results "the weeks and months ahead." Microsoft also gave an update on its transition of Yahoo's ad system to Microsoft adCenter, saying that the two firms are still hoping to transition to adCenter later this fall.