To those who traffic in humans, the slaves are nothing but cargo.
Undocumented workers, lured to the United States with the promise of a better life, often end up being sold into slavery.
The traffickers take extraordinary measures to get the workers inside the United States.
Some come hidden in shipping containers, stashed under the flatbeds of pickup trucks, or packed like sardines in the trunks of cars. Others are even rolled up in carpets.
Smugglers and those who traffic slaves prey on the desperate.
"It's almost always based upon a vulnerability. Poverty, despair, poor education, little prospects," said Wan Kim, the assistant attorney general in charge of the Justice Department's Civil Rights Division.
"Again, everyone trying to reach for the brass ring -- and that is America for many people across the world," Kim continued. "And so when they get a hope of an opportunity to do something significant, to make a life for themselves, in many cases to help bring money back to the family that they're leaving behind -- they jump on it, and they're lead by deceit to come to America and then all the promises are broken."
In an effort to crack down on smugglers, the Justice Department has set up 42 task forces nationwide to work with state and local officials.
From 2001 to 2006 the department prosecuted 360 people for human trafficking and modern day slavery -- a 300 percent increase over the previous six years.
To date the government has helped more than 1,000 victims from 72 countries escape the multibillion dollar smuggling industry that fuels modern day slavery.
The numbers are staggering.
Government estimates say 800,000 people are bought, sold and smuggled worldwide annually. As many as 18,000 of them make their way to the United States from all corners of the world from at least 72 countries, including Cameroon, Egypt, Indonesia and Korea.
Dozens of smuggling rings identified by the government traffic people in the United States, part of what is now a multibillion dollar black market industry.
Kim noted, "This may be the second or third most lucrative underground activity in the world."
"If you think about the typical underground illegal activity -- selling guns, selling illegal drugs -- once you sell the contraband, it's gone. You get the money and then you go find some more contraband to sell. Selling a human being is something that can be done over and over and over again. A woman forced into prostitution can generate thousands of dollars per night."
In 2005, the government convicted members of the Carreto smuggling cartel of promising scores of poor women from Mexico marriage and a chance for a better life in America, only to force them into sexual slavery in Queens and Brooklyn, N.Y.
The women -- some forced to work in a filthy brothel -- were told to charge johns $25 to $35, of which they didn't see a penny.
They were also beaten to keep them under control, and their movements were restricted.
"This kind of modern day slavery is hard to imagine in the United States. I think these cases are so painful to see, and it's often hard even for the victims to recognize that they are victims," said Julie Myers, assistant Homeland Security secretary in charge of Immigration and Customs Enforcement or ICE.
"It's disgusting," Myers said.