Mariah Carey is lending her voice to help find a 13-year-old fan who vanished more than a month ago while walking her dog.

Carey filmed a public service announcement that was to begin airing this week in Los Angeles. The singer got interested in helping after she heard about Christina Williams' disappearance."I do what I do for my fans, and if someone is in need of help the least I can do is draw attention to the case," Carey said Tuesday.