WASHINGTON (AFP) - Would-be immigrants and asylum seekers are being detained for long periods, sometimes years, at US centres as their cases navigate the legal system, Amnesty International USA said in report here. Those being held "include asylum seekers, torture survivors, victims of human trafficking, longtime lawful permanent residents, and the parents of US citizen children," the group said in a 51-page report. US detention of immigrants has tripled since 1996 to some 30,000 people in 2008, the group said in their report titled "Jailed Without Justice: Immigration Detention in the USA," out the other day. "Numbers are likely to increase in 2009," the report read, adding that many of those being held have difficulty obtaining legal aid. While the US Immigration and Customs Enforcement (ICE) reported an average detention stay of 37 days in 2007, immigrants "may be detained for months or even years" as they navigate the legal system, Amnesty said. The group said it found several cases of people who were held for four years while their cases were sorted out. Those being held while their cases are handled are sometimes kept along with criminals, which Amnesty says is a violation of international standards. "America should be outraged by the scale of human rights abuses occurring within its own borders," Larry Cox, executive director of AIUSA, said in a statement. "The United States has long been a country of immigrants, and whether they have been here five years or five generations, their human rights are to be respected," he said. Because of poor medical attention, 74 people have died while in immigration detention over the past five years, the report read. And would-be immigrants who lose their cases "may languish in detention indefinitely if their home country is unwilling to accept their return or does not have diplomatic relations" with Washington, the report read. According to ICE about 40 percent of those held at detention centres are "criminal aliens" - a broad term that includes immigrants awaiting deportation after serving US prison sentences to permanent residents being deported for serious traffic offences. To meet the increasing demand for space, officials have contracts with some 350 local criminal jails across the country to hold immigration detainees. One 26-year-old Chinese woman arrived in the United States in January 2008 seeking asylum after she and her mother were beaten in their home for handing out religious fliers. The woman, who was not named, was first held at the airport, then moved to a county jail. An ICE official ordered her held on a 50,000 dollar bond - something her US relatives took until December to post, Amnesty said. The group also found that conditions in many of the detention sites "do not meet either international human rights standards or ICE guidelines." Immigration detainees are dressed in prison uniforms and often held "in jail facilities with barbed wire and cells, alongside those serving time for criminal convictions."