Mariah Carey and Nicki Minaj are reportedly already causing tension on the American Idol set.

During the first day of taping American Idol's upcoming twelfth season in New York City on Sunday, Carey and Minaj "went at it" and continuously talked over one another while critiquing auditioneers from the judging panel, TMZ reported.

Once Minaj would begin commenting on a singer's performance, Carey would reportedly interrupt her to voice her own opinion. In return, according to TMZ, Minaj would repeatedly just talk louder to drown out Carey's many interjections.

"These girls just don't like each other," a source told the website about the two newly-announced Idol judges, who allegedly both tried to hide the fact they don't like each other.

When Carey -- who formally signed on as an Idol judge in July following the departures of Jennifer Lopez and Steven Tyler -- reportedly discovered Minaj was at the top of Idol producers' lists to join her on the panel in late August, she hung up the phone.

According to TMZ sources, Carey was "led to believe" she would be -- similar to Lopez -- the only woman on the judging panel. In addition, the sources also suggested Carey wasn't pleased Minaj is 13 years younger than her.

Fox announced Sunday morning that Minaj, a rapper, and country singer Keith Urban officially inked deals to serve as new Idol judges next season alongside Carey and returning judge Randy Jackson.

Fox's announcement brings an end to months of rumors and speculation about American Idol's twelfth-season judging panel and gives the reality singing competition a four-judge panel for the first time since Jackson, Simon Cowell, Ellen DeGeneres and Kara DioGuardi served as the show's ninth-season panel in 2010.