President Trump, with a tweet Monday, made a growing immigration issue seem increasingly insidious.

Trump claimed that a caravan of migrants heading north from southern Mexico included "unknown Middle Easterners." By Tuesday, Trump admitted he had no proof to back up that claim, but insisted it could be true.

But U.S. Rep. Lou Barletta, Trump's favorite congressman in Pennsylvania, on Wednesday claimed he had the proof.

"We know there are Middle Easterners in there," Barletta told PennLive during an editorial board meeting. "We know that not all of them have come from Honduras or Guatemala or El Salvador. We know that. We know that for a fact. I'm on [the] Homeland Security [Committee]. I serve on the counterterrorism and intelligence subcommittee. I have a little more information than you do."

So what information does Barletta, a Republican challenging U.S. Sen. Bob Casey's bid for a third term, have to support his own claim?

Barletta's campaign initially cited as an answer an Axios story posted Tuesday, which included tweets from Tyler Q. Houlton, press secretary for the Department of Homeland Security, asserting that "citizens of countries outside Central America, including countries in the Middle East, Africa, South Asia, and elsewhere are currently traveling through Mexico toward the U.S."

But Trump, who made the initial claim, admitted Tuesday afternoon during a discussion with reporters in the Oval Office that "there's no proof of anything" regarding the origins of people in the migrant caravan. He continued, "But there very well could be."

Trump, walking back his claim, noted that the U.S. Border Patrol previously reported intercepting people in the past from Middle Eastern countries attempting to enter the United States through the southern border.

Barletta's campaign, when asked about Trump's walk-back, noted that the four-term congressman from Hazleton had, later in in his PennLive interview, noted that the U.S. government knows little about the people in the caravan. And the campaign pointed to a 2015 DHS report about the origins of people trying to enter the country.

>> VOTERS GUIDE: View candidates in the 2018 midterm election based on your address, or browse all the action in Pennsylvania, New Jersey, and Delaware

>> SIGN UP: Get daily text messages on key issues leading up to the election

“I’m glad that we have a president who says, ‘You’re not just going to march into the United States without us knowing who you are,’” Barletta told PennLive. “That’s reasonable.”