From this:

Congressman Tom Tancredo (R-CO) today revealed figures which show that since October, 2004, 51 persons who have crossed into the U.S. illegally were arrested on suspicion of terrorism. The figures, part of a Department of Homeland Security response to a inquiry by the Congressman, document the national security risk our porous borders pose on the eve of Congress' first attempt to rewrite immigration law in nearly a decade.

Federal law enforcement coordinates its terrorism efforts through "Joint Terrorism Task Forces" (JTTFs), which include officials from the Justice and Homeland Security Departments. Since October, 2004, JTTFs have kept track of arrested terrorist suspects who are in the U.S. illegally. The JTTF document shows 51 persons were arrested who had "entered without inspection" into the U.S. from countries such as Iran, Iraq, Lebanon, Egypt, Syria and Pakistan...

"Entered without inspection" means crossing the border illegally, or otherwise sneaking in not at a port of entry.

A table showing the arrests, what they were arrested for, and their countries of origin is in this PDF file. A key for the U.S. Code sections is in this .doc file.

In the PDF file, those with "EWI" in the status column are the illegal crossers.

And here it was just Sunday when Ed Bradley assured us no terrorists had come over the border.

UPDATE: Tancredo may or may not have jumped the gun. The Denver Post salivates in "Tancredo releases miscast terror data" that the DHS claims that none of the 51 were arrested on terrorism charges, they were only arrested for illegal entry. However, they were investigated for links to terrorism:

The suspects were investigated by federal terrorism officials because they came from "countries of interest," such as Iran, Iraq, Lebanon and Syria, the FBI said.

"I'm unaware of any instances at this time of individuals that have been charged with terrorism-related offenses (among) individuals who have been smuggled across the border," said FBI spokesman Bill Carter.

However, neither he nor a spokesman from U.S. Immigration and Customs Enforcement could rule out any ongoing terrorism investigations involving any of the 51...

..."I'm somewhat disappointed that Homeland Security is somewhat afraid of talking about it straight out," [Tancredo] said when told of the agency's statements.

Asked about his press release saying that the suspects had been arrested on terrorism-related charges, Tancredo said, "We shouldn't have been probably so definitive in that, and I'm sorry we did that. I take responsibility for that."

Nevertheless, Tancredo said, the data are the first evidence that people in the country illegally are being investigated for possible terrorism connections...