WASHINGTON (CBS DC) — Rep. Duncan Hunter, R-Calif., says that at least ten fighters for the Islamic State of Iraq and Syria have been apprehended while attempting to enter the southern U.S. border.

The California Republican claims that “at least ten ISIS fighters have been caught coming across the Mexican border in Texas,” in a conversation with Fox News on Tuesday. Hunter says that the Islamic terrorists are slipping into the U.S. through the porous southern border as several have already been captured.

“There’s nobody talking about it,” Rep. Hunter told Fox. “If you really want to protect Americans from ISIS, you secure the southern border. It’s that simple…They caught them at the border, therefore we know that ISIS is coming across the border. If they catch five or ten of them then you know there’s going to be dozens more that did not get caught by the border patrol.”

In August, Chairman of the Joint Chiefs of Staff, Gen. Martin Dempsey, warned that the open border posed an “immediate threat” for terrorist activity infiltrating the country. The government watchdog group, Judicial Watch, said ISIS terrorists were “planning to attack the United States with car bombs or other vehicle born [sic] improvised explosive devices.”

Hunter, a member of the House Armed Services Committee, said that the 1,933-mile southern border with Mexico is the obvious entry point for Islamic State terrorists. He says that information regarding the capture of Islamic State terrorists crossing the border comes directly from U.S. Customs and Border Protection.

“ISIS doesn’t have a navy, they don’t have an air force, they don’t have nuclear weapons. The only way that ISIS is going to harm Americans is by coming through the southern border – which they already have,” he added.

“They aren’t flying B-1 bombers, bombing American cities,” said Hunter. “But they are going to be bombing American cities coming across from Mexico…All you have to do is ask the border patrol.”

The Department of Homeland Security released a statement on Wednesday that claims alleging Islamic State militants have been apprehended at the Mexican border are “categorically false.”

“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.”

After Hunter’s comments to Fox, one of his sources nuanced their claims, saying that some of those apprehended at the border might be ISIS-affiliated or possibly Americans who fought with the Syrian Free Army – one of many ISIS enemies.

In a statement to ABC News, a spokesperson for Hunter said he was not backing down on the claims.

“The Congressman was conveying what he knows — and what he was told,” the spokesperson told ABC. “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.”

— Benjamin Fearnow