Some viewers who watched Mariah Carey sing a medley of her biggest hits during last night's American Idol series finale wondered if Carey lip-synced her performance. Her voice at times reportedly failed to match the audio the audience was hearing.

Carey stepped onto the American Idol stage shortly after the finale's broadcast started. While many of Carey's fans praised her highly anticipated performance, some questioned whether her singing was authentic. Fans flooded Twitter with tweets questioning her performance.

"Mariah Carey, if you are going to lip sync on American Idol, at least attempt to make it look real. Or don't perform on behalf of America," tweeted a viewer who goes by the handle @JadenStyles.

"She ABSOLUTELY DID NOT lip-sync," said her spokesperson. "She performed LIVE in front of several thousands of people!!!! (and did it 3 times!!)."

The rep for the 43-year-old R&B singer and Idol judge confirmed that Carey did sing to a prerecorded track, a common practice even among big-named artists in the music business. The spokesperson also clarified that Carey "performed with a 40-person choir" and "SANG LIVE" in front of thousands of people, and did it three times.

The rep added that Carey sang three additional hits that were not part of the medley to entertain the Idol crowd between live shots.

Carey wasn't the only Idol  team member to take the stage. Jennifer Lopez, a former judge on the TV show, returned and performed her new single Live It Up with rapper Pitbull.

Others who performed in the Idol finale included Gangnam Style singer Psy, season 8 runner-up Adam Lambert and panel judges Keith Urban and Randy Jackson.

When asked if there were any possible audio issues on its end, Fox had no comment.