JERSEY CITY, N.J. (CBSNewYork)Donald Trump insists he saw thousands of Muslims in Jersey City celebrating as the Twin Towers fell on 9/11. But is there a single shred of evidence to back his claim?

The Republican presidential hopeful made the controversial comment during a campaign rally in Alabama on Saturday night, CBS2’s Dick Brennan reported.

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“I watched when the World Trade Center came tumbling down, and I watched in Jersey City, New Jersey, where thousands and thousands of people were cheering as that building was coming down,” Trump said.

He doubled down Sunday on ABC.

“It was well covered at the time,” he said. “There were people over in New Jersey that were watching it.”

But where?

The only video CBS2 found was of thousands of Palestinians cheering the attacks in Jerusalem.

On Monday, Trump tripled down, demanding an apology from critics, pointing to a Washington Post article on Sept. 18, 2001, which he says proves his point.

The article says: “In Jersey City, within two hours of two jetliners plowing into the World Trade Center, law enforcement authorities detained and questioned a number of people who were allegedly seen celebrating the attacks and holding tailgate-style parties on rooftops while they watched the devastation on the other side of the river.”

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But The Washington Post now says there was no source for the information and nothing came of it.

Now Trump has company on the Republican side. Ben Carson says he, too, saw video of Muslims cheering the 9/11 attacks in New Jersey.

When asked where he saw the video, Carson answered: “The news reels.”

In the meantime, at least one Democrat is questioning Trump.

“I have not heard any evidence of this happening,” presidential candidate Bernie Sanders said. “I don’t know where Mr. Trump gets his evidence, what he has seen, but I don’t think anybody else in America has seen it.”

New Jersey Gov. Chris Christie, who’s also running for president, said he doesn’t recall Muslims cheering on 9/11 and if it happened, he would remember it. But Christie then hedges and says there could be things he’s forgotten from that time.

Since the terror attacks in Paris, Trump has actually increased his lead in the GOP race.

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“It’s very clear that he’s tapping into sentiment in the American public that may not be very widespread, but it’s certainly there within a certain segment of the electorate,” said Costas Panagopolus, director of the Center for Electoral Politics and Democracy at Fordham University. “The more he enunciates and articulates those views very explicitly, the more enamored with him that segment of the population will become.”