Human rights lawyers often refer to it as "the other Guantanamo," "Guantanamo's evil twin" or "Obama's Gitmo" — an attempt to raise the profile of the U.S. detention facility in Afghanistan that few know about.

It's official name is the Bagram Theater Internment Facility. And even though it was recently rebuilt and renamed the Detention Facility in Parwan, after the province, most continue to refer to it simply as Bagram.

Run by American troops, the prison is located on the Bagram Air Base, about 80 kilometres north of Kabul, in a cavernous aircraft hangar built in the 1980s following the Soviet invasion of Afghanistan.

In 2002, the U.S. military opened the prison doors to "enemy combatants" as part of its war on terror and it quickly became their largest detention centre in the war-torn country.

By 2005, the population had swelled to more than 800 alleged insurgents. It hovered around 600 detainees from 2006 to 2009, but in the past two years that number has quadrupled.

The latest figures from Joint Task Force 435, the military unit in charge of Bagram, state that more than 2,400 individuals were being held by the U.S. in Parwan as of Aug. 31, 2011. About 350 others were in the Afghanistan-operated section.

The population

The majority of detainees held in Bagram are Afghans, though specifics about the prison population are difficult to obtain due to U.S. secrecy surrounding the facility.

A U.S. military guard watches over detainee cells inside the Parwan detention facility. Dar Yasin/AP

Only once, in January 2010, has the American military released the names of detainees held there. The largely redacted list, requested by the American Civil Liberties Union, dislosed the names of 645 detainees held as of Sept. 22, 2009.

In 2006, the U.S. military stated that about 40 detainees were foreigners, mostly Pakistanis. No updated numbers have been given, but human rights lawyers independently compiling the information about the detention population estimate it has now risen to at least 50, not including detainees who briefly spent time in Bagram before being transferred to another facility such as Guantanamo.

Human rights lawyers say a handful of detainees were also detained there after having been captured in other countries.

Two Canadians are known to have been held at Bagram. Toronto-born Omar Khadr was there for about four months before he was taken to the Guantanamo Bay naval base in Cuba.

Another case, which recently emerged from U.S. diplomatic cables published by WikiLeaks, was that of a mentally ill Canadian-Egyptian man, Khaled Samy Abdallah Ismail, held at Bagram for more than 18 months.

Tina Foster, executive director of the International Justice Network, says the organization believes other foreigners detained at the Bagram facility include at least 35 Pakistanis, one Tunisian and two Yemenis.

History of torture

In the early years of operation, the Bagram facility became notorious for abuse. Two detainees died in the Bagram facility in 2002 after being beaten by American soldiers. Recent accounts by former detainees describe improved conditions, but allegations of torture persist.

"Torture was something very common with all of us," says Ghairat Baheer,a Pakistani doctor who was held at several prisons, including Bagram, from 2002 to 2008.

Reports also surfaced in 2010 about mistreatment of Afghan detainees at a "secret jail" at the Bagram Air Base.

An August 2009 report by the then commander of American forces in Afghanistan, Stanley McChrystal, stressed that Afghan people saw U.S. detention operations as "secretive and lacking in due process."

McChrystal went on to note that "detention operations, while critical to successful counterinsurgency operations, also have the potential to become a strategic liability for the U.S. and ISAF (the international forces)."

His assessment found that captured Taliban and al-Qaeda leaders were operating within prison walls and creating future insurgents out of petty criminals; also that the Afghan people's negative perception of the detention operations was fuelling anti-American sentiment.

The new facility

For human rights lawyers, the issue is less perception than that the U.S. government is holding detainees for lengthy periods of time without charge or access to lawyers.

As McChrystal stated in his report, the government does have the goal of "getting the U.S. out of the detention business" by handing over control of Bagram to the Afghan government.

Plans to hand over the facility were delayed until at least 2014, when the last foreign troops are scheduled to leave the country.

Changes have taken place at the Bagram Air Base in recent years. Among them is the replacement of the decrepit Bagram detention centre — and its 60-foot wire mesh "cages" — with a new $60-million facility containing 56 cells and a library.

A new detention review process also went into effect at the facility. Within two months of incarceration, detainees must be given a case review, with followups every six months or so. Detainees are assigned a U.S. military officer who gathered information on their case and advocates for their release. Previously, detainees had no right to hear the evidence against them.

But even though the U.S. has been cleaning up Bagram's image and departing occasionally from the intense secrecy surrounding the facility, many questions remain about what has gone on inside its walls.