U.S. Immigration and Customs Enforcement is holding an untold number of people in secretively maintained detention facilities all over the United States, according to a report set to be published next year in The Nation.

Many of the sites are unmarked and unlisted, going unnoticed in office parks and commercial zones, according to reporter Jacqueline Stevens. The so-called ICE "subfield offices" are mainly used to house prisoners in transfer and are not subject to the basic standards applied to ICE and even military prisoners.

At a subfield office known as B-18, located near a Los Angeles federal building, ICE keeps immigrant prisoners in "a barely converted storage facility."

"You actually walk down the sidewalk and into an underground parking lot. Then you turn right, open a big door and voilà, you're in a detention center," explained Ahilan Arulanantham, an ACLU immigration attorney interviewed by The Nation. "Without knowing where you were going, he said, "it's not clear to me how anyone would find it. What this breeds, not surprisingly, is a whole host of problems concerning access to phones, relatives and counsel."

The report continued: "B-18, it turned out, was not a transfer area from point A to point B but rather an irrationally revolving stockroom that would shuttle the same people briefly to the local jails, sometimes from 1 to 5?am, and then bring them back, shackled to one another, stooped and crouching in overpacked vans. These transfers made it impossible for anyone to know their location, as there would be no notice to attorneys or relatives when people moved. At times the B-18 occupants were left overnight, the frigid onslaught of forced air and lack of mattresses or bedding defeating sleep. The hours of sitting in packed cells on benches or the concrete floor meant further physical and mental duress."

One former prisoner who spoke with The Nation said that when she inquired how long she would be held, guards laughed at her. "I was thinking these people are going to put me and the other people in a grinder and make sausages and sell them in the local market," she reportedly said.

A list of the 186 facilities is available here [PDF format].

Read the full report here. The next edition of The Nation is due out Jan. 4, 2010.