For many people around the world, the U.S.-Mexico border is a doorway to opportunity — one that's unlocked and wide open.

Brazilians, Chinese, Pakistanis and many others are joining the tide of Mexicans who sneak across every day.

"OTMs include people from all over the world — South America, the Middle East, the Caribbean," explained former Immigration and Naturalization Service Special Agent Michael W. Cutler, currently a fellow at the Center for Immigration Studies (search). "Anyone other than Mexican is an OTM."

In 2001, 5,251 "OTMs" were caught crossing over from Mexico. Last year, the number was more than 35,000.

In the first eight months of this fiscal year, it's up to 70,000 already — 230 people a day — and they're only the ones getting caught. Hundreds more make it across undetected, experts believe.

"The vulnerability of a porous border is a security problem, and we always have to be concerned that the real bad guys will exploit those vulnerabilities," said Frank Sharry, executive director of the National Immigration Forum (search).

Critics are concerned at the way OTMs are handled.

Mexicans are processed and sent back across the border within a few hours but Mexico won't allow the United States to send them citizens from other countries — and under U.S. law, they're entitled to a deportation hearing (search).

Because the immigration service lacks prison beds to hold them, the vast majority of OTMs are released from custody and asked to voluntarily return for their court date — which the majority of them do not do.

"They are given a piece of paper called a notice to appear, which administratively starts the ball rolling for a deportation hearing," said Cutler. "Not surprisingly, fewer than 15 percent show up."

"Our bureaucracy is not up to the challenge of protecting this country, our congress is not dealing with the reality in a 21st-century way, our immigration laws are terribly out of place," commented Sharry.

So what's the answer? While some say more legal immigration is needed, others want the borders effectively closed. Both sides seem to agree that giving illegal immigrants a free pass is no solution at all.

Click in the video box above to see a full report by FOX News' William La Jeunesse.