DENVER -- A loophole in the law has allowed untold numbers of undocumented immigrants to incorporate in Colorado without a green card, Social Security number or even a Colorado driver's license. While some see it as an immigration issue, others realize the implications reach much further, citing national security.

Like anyone else who sets up a business in Colorado, most illegal immigrants are simply trying to build a better life.

The problem is they are indistinguishable from others who may want to do harm.

For smugglers, money launderers or terrorists, it would be easy to set up a business in Colorado full of operatives.

"So he's here basically undocumented? That's OK, we're here to help," said an employee of an accounting firm in Lakewood.

He was talking to a 7NEWS employee and in front of a hidden camera.

"We'll give you a very good record so that if the state were to ask, the federal were to ask to do your income tax at the end of the year, it's smooth sailing," said the employee, named Ralph.

The accounting office is called Administrative Concepts.

It has helped hundreds of people, including many illegal immigrants, set up legitimate corporations in Colorado.

It's a prime example of a major homeland security loophole.

"They can set up any kind of business they wanted to and they could hide here for years with us not knowing who they are," said Jeff Copp, the agent in charge of Denver's Immigration and Customs Enforcement office.

CALL7 Investigator John Ferrugia asked, "Essentially, I can set up a business in this state, or many states, without a Social Security number, without a driver's license and without a green card?"

Copp responded, "That's correct."

CALL7 Investigators have been tracking hundreds of small Colorado corporations, some of them one-man companies, set up by the Lakewood accounting firm.

"I'm John Ferrugia, are you the roofer?" Ferrugia asked one man outside the firm.

The man, whose brother owns a corporation in Colorado, was there to pick up a paycheck.

"Your brother doesn't live here?" asked Ferrugia.

"No, he's in Mexico," replied the roofer who also admitted his brother is not a U.S. citizen nor does have any U.S. identification.

Our investigation found that his brother set up a legitimate Colorado corporation using what is known as an "Individual Tax Identification Number," or ITIN.

According to the Internal Revenue Service, to get an ITIN to pay business taxes, you need as little as two forms of identification and it can be foreign ID, including a foreign driver's license, foreign birth certificate or even a foreign voter registration card.

"The person puts that information on the form and we send it to the government," said Gil Johnson, the owner of Administrative Concepts in Lakewood.

He freely admits he has no obligation to know or to check whether the documents used to set up the corporation are valid.

"I could submit a number of things to you that you could never check?" asked Ferrugia.

Johnson replied, "Absolutely. We don't know if the document is valid."

Johnson is not alone.

National firms in predominately Hispanic neighborhoods in Denver advertise saying they can help set up businesses using an ITIN.

CALL7 Investigators have also discovered some clients of Administrative Concepts who set up businesses using Social Security numbers that are being used by others.

Johnson said, "There's no access for us to check anything. We just submitted it."

"You can find out if it was a valid Social Security number, but you couldn't necessarily find out who it belonged to?" asked Ferrugia.

Johnson replied, "No, we do not have access."

Copp reinforced the statement and told 7NEWS, "He doesn't have to verify that Social Security number actually belongs to you. As long as it is a good workable Social Security number then it's usable."

"He can open the business?" asked Ferrugia.

"Right," answered Copp.

Using a hidden camera, we learned how Ralph, a bilingual employee at the accounting firm, coached illegal immigrants on how to set up a legitimate business.

"The ITIN number? We can process it for him. He can also do it through the Internet. We've been processing a lot of them because we know the requirements," said Ralph.

Ferrugia asked Johnson, "If I come in and I'm here illegally, I say so, and I want to set up a business, what does Ralph tell me? Or what should he tell me?"

Johnson said, "Ralph would tell you that we cannot help you, in any way."

But, in front of the hidden camera, Ralph suggests that if not an ITIN, the man can set up a company with his companion's legitimate Social Security number.

"If it runs on your number, you set up the company, there's not going to be any problem. Nobody needs to know that he's not the owner," said Ralph.

Copp said he believes sending illegal immigrants to set up their own business takes the pressure off employees who are required to verify information and, Copp said, the situation presents major national security concerns.

Ferrugia asked, "Easy for a terrorist organization to set up shop here?"

"It could be easy for anyone to set up shop here," said Copp. "It would be an easy way to create a business and to hide your assets in whatever criminal activity you are involved in. I see it as a huge vulnerability for the country."