Huge profits are being generated by some of the countries largest prison companies, as the country incarcerates more illegal immigrants than at any time previously.

The cost to taxpayers in the U.S. could top the $2 billion mark in 2012. The prison companies are expecting to receive their biggest cut in the next few years as new facilities are planned by the government to house the more than 400,000 undocumented immigrants detained each year.

After more than 10 years of expansion, the private, sprawling system runs different detention centers from an industrial site flanking the airport in Newark to a suburb of Denver and only three companies control the majority of it.

The growth will continue, despite the steep drop off in illegal immigrants coming into the U.S. over the last few years. During 2011, almost half of the beds in the civil detention system in the U.S. were located in private facilities with oversight by the feds very limited. Just 10 years ago, the rate was only 10%.

The companies are raking in cash from other subsidiaries that help provide transportation and health care to the detainees. In addition, they are holding even more immigrants in their private prisons that have been convicted of federal crimes. The recent financial boom has been a salvation for the companies, which at one time were near bankrupt even though officials in the federal government know that privatization of prisons, is not necessarily the cheapest way to go.

The shift toward prison privatization happened very quietly, while the unsuccessful efforts by the Congress to overhaul the immigration laws were in the headlines from coast to coast sparking huge demonstrations while negotiations by lawmakers to increase dollars for detention costs received hardly any attention.