Google placed a text ad above the image titled "Offensive Search Results" that states "Sometimes our search results can be offensive. We agree."
Users who then click on the ad are directed to a letter from Google that explains its results "can include disturbing content, even from innocuous queries" but notes that Google doesn't endorse content on these Web sites.
Google says its search formula relies on thousands of factors to rank a Web page's importance, and says it doesn't eliminate search results simply because of user complaints. However, Google says it will take down images in certain cases, such as when required by law to do so.
"We apologize if you've had an upsetting experience using Google," the company wrote.
Mountain View, Calif.-based Google also posted about the issue in a user support forum.
Spokesman Scott Rubin would not elaborate on how the image ended up as the number-one result for the first lady. He said the company did remove one site displaying the image from its results because it included viruses, which Google policy prohibits. But a different Web site later posted the same image, he said.
The White House declined to comment.
This is not the first time Google has apologized for content in its search results. The company issued a similar response in 2004 when the top result for the term "Jew" pointed to an anti-Semitic Web site.