The Obama administration on Tuesday unveiled preparations to permit additional nonviolent illegal immigrants to await deportation proceedings wearing ankle bracelets outside prison walls rather than locked up in costly jail cells. Federal officials said reducing the number of imprisoned immigrants without criminal records would save money, keep families together and ease complaints about unnecessarily harsh prison conditions raised by some immigrant advocacy organizations. 'This is a system that encompasses many different types of detainees, not all of whom need to be held in prison-like circumstances or jail-like circumstances,' said Homeland Security Secretary Janet Napolitano. High security 'not only may be unnecessary but more expensive than necessary,' Napolitano added. The Immigration and Customs Enforcement agency known as ICE detains nearly 400,000 foreign nationals on suspected immigration violations each year at a cost of $2.4 billion. On a typical day, about 31,075 immigrants are held at more than 300 federal, state, local and private prisons across the country. The agency simultaneously tracks another 19,169 immigrants released into so-called 'alternative to detention' programs that include telephonic reporting, global positioning tracking using devices such as ankle bracelets, curfews, unannounced home visits and employment verification. Of the foreign nationals held on a typical day, the majority were deemed 'low custody -- or having a low propensity for violence,' said an investigative report used as the basis for the planned changes. Most detainees are held for about 30 days before their immigration status is adjudicated and they face possible deportation. The Obama administration will submit to Congress by mid-December a 'nationwide implementation plan' to expand the number of immigrants under federal supervision while awaiting deportation, Napolitano and ICE chief John Morton said at a news conference. Neither official detailed the size of the proposed expansion. Prison costs the federal government about $100 a day for each detainee compared to $14 a day for community-based supervision, Napolitano said. Morton said he also would begin exploring the possibility of moving noncriminal, nonviolent detainees into unused residential facilities, including former hotels and nursing homes. 'These reforms will address the vast majority of complaints about our immigration detention, while allowing ICE to maintain a significant, robust detention capacity to carry out serious immigration enforcement,' Morton said. The Obama administration's effort to revamp the immigration detention system stems from complaints and costs that arose during the Bush administration's post-9/11 crackdown on illegal immigration. The Bush-era campaign contributed to a four-fold increase in the number of imprisoned detainees awaiting deportation proceedings since the late 1990s. Immigrant advocacy organizations also challenged the medical care being provided to detainees. At least 104 detainees have died in federal custody since 2003 -- most recently Ruben Sandoval, 21, a Guatemalan national who died of cancer-related complications at a hospital in South Carolina on Sept. 30. Sarnata Reynolds, policy director for immigrant rights at Amnesty International, said her organization was 'encouraged' by Napolitano's decision to 'find new environments for immigrants that will not require prison jumpsuits and jail cells.' Reynolds added: 'Thoughtful, effective and low-cost alternatives to detention exist, but they remain under utilized.' Both Napolitano and Morton emphasized that detention would remain a cornerstone of immigration enforcement as the Obama administration moves ahead with plans to pursue comprehensive immigration reform, possibly late this year. 'We need to make sure we are covered as we look at alternatives to detention so that those who are given (alternatives to detention) are not going to use that to escape or get into the general population in way that we can't quickly find them and get them back,' said Napolitano, a former governor and attorney general of Arizona. 