Tom McNamara and the Eyewitness News 4 Investigators have spent the last three months talking to experts and eyewitnesses.

The stories are compelling and the evidence is frightening, and just this week, Colorado Congressman Tom Tancredo released a report showing that the problem is worse than anyone thought.

Here's what the Eyewitness News 4 Investigators uncovered.

"It's a Muslim prayer blanket. It was found about a mile and a half west from the Douglas port of entry in 2001."

Larry Vance is a rancher who lives near the U.S.-Mexico border in Douglas, Arizona.

For years, he says he's watched - and documented - thousands of illegals crossing the border and running away to eventual arrest... or freedom and anonymity somewhere in this country.

And in just one hour, during this stake-out along the border between Douglas and b\Bisbee, The Investigators count 198 illegals in five different groups crossing into the U.S. with no resistance.

Watch as they huddle in the bushes, then climb thru a few strands of barbed wire and run for freedom.

We called Border Patrol and waited another full hour, but no one ever came.

Later, we checked Border Patrol logs which note agents being dispatched following our call, but also note those agents found no signs of activity in the area.

In recent years, Vance says, the evidence some illegals leave behind is alarming.

Vance says, "Other log books, diary-type things, other bits and pieces of paper with Arabic written on them found in the area over the last few years

We've all heard of the U.S. government's Terror Watch List: countries flagged because Americans are endangered by their citizens, yet regularly, illegals from those countries are crossing the Arizona border, blending in with groups of Mexican and South American illegal immigrants.

If apprehended, they are brought to this federal detention center in Florence, Arizona.

The investigators found that on this day, several individuals of this kind were being detained here, including some from Sudan, Iran, and even Iraq.

These are just the ones who were caught.

These detainees are called 'other than Mexicans' or OTM's. Most will eventually be sent back to their home country.

But some disappear very quickly, usually before they even reach this center or other holding facilities. They're taken away by tight-lipped federal agents to who-knows-where.

Who are they? They're called 'Special Interest Aliens" or "SIA."

According to Ben Anderson, a retired U.S. Army Colonel, The SIA that they don't want to talk about. That's special interest alien. These are people from those countries that we consider terrorist threats."

Anderson is a retired U.S. Army Colonel who tracks illegal immigration from his home in Sierra Vista, Arizona. He has a website sharing his research into Special Interest Aliens.

"You will not read about that. You will not hear about that. They will not talk about that. They will not provide that info to the press

Colonel Anderson says these Special Interest Aliens originate in the Middle East or Northeast Asia. They travel through Spain to what's called the tri-border area of Brazil, Argentina, and Uruguay, then, to Mexico City.

They pay to learn Spanish language skills, and by the time they reach the U.S., they're acting and talking like Mexicans to fool border agents.

And, Anderson says, they're entering the United States right through our backyard. "This is the main alley. It's called "Cocaine Alley" or "Terrorist Alley." Whatever you want to call it, Arizona is the prime place."

Cochise County is the center. It's the point of gravitus, center of gravity for all illegals," says Anderson.

Anderson says some Special Interest Aliens are well-funded. paying tens of thousands of dollars to be smuggled into this country. They manage to get passports from non-terrorist nations.

And here's the shocking part: if they are caught, they are often released on their own recognizance, never to be seen again.

According to Retired Border Patrol Agent David Stoddard, "There are Middle Easterners coming across the border as we speak."

Stoddard agrees with Anderson. Stoddard spent 17 years as a Border Patrol agent and supervisor in the Tucson Sector before retiring.

"What's scary is that I can show you places out here on the line right now where 18-wheelers can be driven across."

"These 18-wheelers can be loaded with anything -- illegal aliens, atomic weapons, whatever."

Stoddard says Americans would be shocked if they knew just how many people from all over the world are getting into this country across the Arizona border. And he says we're even less safe from terrorism today than we were before 9/11.

Take for example, the capture of terrorist suspect Jose Padilla (pictured at right). The Justice Department says Padilla and an accomplice planned to enter the U.S. thru Mexico to blow up apartment buildings in major cities, like New York.

Or the case of suspected al-Qaeda sleeper agent Mohammed Junaid Babar.

Babar has told investigators of a scheme to smuggle terrorists across the Mexican border. He's tied to a terror plot to carry out bombings and assassinations in London.

And the Tombstone Tumbleweed newspaper reports that in June, 53 Middle Eastern men were apprehended by Border Patrol agents near Willcox.

It's believed they were from Iran or Syria.

Stoddard says, "It's the ones who are sneaking into our country under cover of darkness between our ports of entry that concern me and should concern every American.

Border Patrol Council President T.J. Bonner says, "You don't know what is getting by you unless you come across, as you said, small pieces of evidence, remnants of things that give you clues, that not everybody is coming across from mexico looking for a job."

Bonner knows exactly who and what current agents are uncovering along our border and he has a dire warning:

"It's only a matter of time before another terrorist attack occurs, unfortunately.

Some in Congress are starting to take notice of the threat. Colorado Congressman Tom Tancredo released a report that revealed a 50% increase in OTMs, illegals Other Than Mexicans, crossing the border.

Tancredo says some illegals from terrorist nations are paying as much as $50,000 to be smuggled in. He says they're not paying that kind of money simply to work at a 7/11.

See another story on this from the UK Telegraph News