Critics of a pair of federal immigration detention centers in Georgia are asking for a congressional investigation on whether they should be shut down.

A coalition of civil and immigrant rights groups including the American Civil Liberties Union Foundation of Georgia say the privately-run Stewart and Irwin County detention centers are holding detainees for too long, treating them inhumanely and violating their constitutional rights. The groups say the remote locations of those centers make it difficult for detainees to stay in touch with their attorneys and families.

In 2012, the ACLU released a report — entitled "Prisoners of Profit: Immigrants and Detention in Georgia" — that is critical of the detention centers. The civil rights group sent a letter to Georgia's congressional delegation Friday, asking for an investigation. The ACLU had not received a response as of Tuesday afternoon.

U.S. Immigration and Customs Enforcement issued a statement Tuesday, saying it had reviewed the ACLU’s 2012 report and found “many of the claims to be unsubstantiated and factually incorrect.” Some of the allegations regarding the Voluntary Work Program at Stewart were substantiated, according to ICE, and “corrective action was taken.”

“The reality is that both the Stewart and Irwin County detention centers have been inspected within the last year and have been found to be in compliance with our rigorous detention standards,” ICE said in its statement. “Since August 2009, ICE has been engaged in a significant reform of the immigration detention system to prioritize the health and safety of detainees in our custody while increasing federal oversight and improving the conditions of confinement within the detention system.”

ICE’s statement continued: “As a part of these reform efforts, ICE management has officers assigned on-site at all of these facilities to continuously assess living conditions, ensure compliance with the detention standards, and observe routine interactions between detention facility staff and ICE detainees. Any allegations of abuse or misconduct by those charged with the health and welfare of ICE detainees are promptly reported to the appropriate entities for immediate review, investigation and action.”