Miss USA -- 2nd Contestant Says Pageant was Rigged

Miss Pennsylvania is finally getting some backup ... because a SECOND Miss USA contestant is now saying there is PROOF the competition was rigged.

Problem is ... the corroborator is not revealing her identity.

FOXNews.com says the network spoke with the mystery contestant ... who says Miss Florida Karina Brez told her she saw a secret Miss USA document which contained the names of the Top 5 finalists ... before the Top 15 were announced.

"I saw Florida backstage and she was very, very flustered and upset. I thought it might be because she didn’t make the top 15 cut, but at that point she was able to reveal to me at least four of the five names who went on to be the top girls," the contestant told FOXNews.

The mystery woman continued, "[Miss FL] couldn’t remember the fifth because she was so upset. Several of the girls then started hearing through the grapevine about a list; a lot of people were upset.”

The story seems to fall in line with the allegations made by Miss PA Sheena Monnin -- who claimed Miss FL told her the same thing while they were backstage. Monnin has since resigned from her post and has given back her crown.

The Miss USA pageant -- and its owner Donald Trump -- have all denied the allegations ... and have taken legal action ... claiming Monnin's claims are just "loser's remorse."

Multiple contestants are also standing behind Trump ... saying Miss PA is a sore loser who made the whole thing up.