Insiders tell TMZ, that Rivera and the rest of the cast reportedly became annoyed with Michele after she walked off set to deal with a personal problem and left everyone waiting to finish a scene. Sources close to Rivera claim she "had the stones" to go tell producers everyone was tired of waiting on Michele.
Later, when the "Cannonball" singer heard about Riveras' complaint she reportedly stormed off the set.
In another version of the story, reported by Hollywood Life, Michele never found out about Rivera's comments and it was Rivera who "showed up to set in really bad shape."
"She went off on one of the producers on the show and they got really upset with her and it escalated from there,” an insider said.
In this version, insiders say that Michele didn't storm off the set, but left with creator Ryan Murphy and another costar to do a previously scheduled live Twitter chat.
Another source tells TMZ that Rivera was fired after the incident.
Neither of the actresses nor FOX has addressed the rumors regarding the alleged altercation.