DHS Rebuffs Congressman’s Claim ISIS Infiltrating Southern Border

— -- The Department of Homeland Security is denying a congressman’s assertion that fighters with the militant group Islamic State, also known as ISIL or ISIS, have been caught crossing the southwestern border.

“The suggestion that individuals who have ties to ISIL have been apprehended at the Southwest border is categorically false, and not supported by any credible intelligence or the facts on the ground,” a DHS spokesman said in a statement today. “DHS continues to have no credible intelligence to suggest terrorist organizations are actively plotting to cross the southwest border.”

Rep. Duncan Hunter, R-Calif., told Fox News on Tuesday night that ISIS is sneaking into the U.S. through the southwestern border.

"I know that at least ten ISIS fighters have been caught coming across the Mexican border in Texas," Hunter claimed. "There's nobody talking about it."

"If they catch five or ten of them, then you know there's gonna be dozens more that did not get caught by the border patrol," he continued.

One source close to Hunter worked to walk back the comment, emphasizing that the congressman received a tip from a “high level” source at U.S. Customs and Border Protection who told him that a group of people with “suspected ISIS affiliation” –- even Americans who traveled to Syria to fight with the Free Syrian Army against President Bashar al-Assad –- were apprehended at the border.

The tip "was from a confidential source with the Border Patrol," the source said in an email. "[It’s] more accurate to say people with known associations. Not 'fighters' in the sense folks might immediately think."

While DHS and several other congressional sources shot down the claim outright, a spokesman for Hunter said that the congressman fears ISIS sympathizers could easily melt into U.S. cities and breed home-grown terrorism.

“The Congressman was conveying what he knows -- and what he was told,” Joe Kasper, deputy chief of staff to Hunter, wrote in response to the DHS denial. “It makes sense that the left hand of DHS doesn't know what the right hand is doing -- it’s been that way for a long time and we don’t expect that to change.”

Customs and Border Protection is part of DHS.

Hunter’s office declined an ABC News request to interview the congressman.

ABC News’ Jeff Zeleny and Mike Levine contributed to this report.