NEW YORK (Reuters) - Organizers of the Miss USA contest on Wednesday raised questions about the credibility of Miss Pennsylvania, a contestant who said this week she was resigning her crown because she believed the contest is rigged.

Sheena Monnin, who represented Pennsylvania in the pageant staged in Las Vegas on Sunday but did not place in the top 16, said on Facebook on Monday she could "no longer be affiliated in any way with an organization I consider to be fraudulent, lacking in morals, inconsistent, and in many ways trashy."

A fellow contestant claimed to have seen a list of the top five winners days before the pageant took place, she wrote in a separate Facebook post on Tuesday.

The Miss Universe Organization said it investigated her claims and found them groundless. The Miss USA winner goes on to represent the nation in the Miss Universe competition.

The organization released a copy of an e-mail it said was sent by Monnin to a regional organizer in which she said she was resigning as Miss Pennsylvania because she objected to a recent decision by organizers to allow transgendered contestants to take part, saying it goes against her "moral fiber."

"Today she has changed her story by publicly making false accusations claiming that the pageant was fixed," the organization said in a statement.

On Wednesday, real estate developer Donald Trump, a co-owner of the Miss Universe Organization, called Monnin's allegations "ridiculous" and suggested she was a poor loser.

"We're going to bring a lawsuit against this girl," he told NBC's "Today" show. "This is a girl who went there, lost, wasn't in the 15, and she's angry at the pageant system."

Asked about a lawsuit, a spokeswoman for the organization said: "We will have to wait to see what happens."

Monnin could not be immediately reached for further comment.