© John Moore/Getty Images NEW YORK, NY - APRIL 11: U.S. Immigration and Customs Enforcement (ICE), officers arrive to a Flatbush Gardens home in search of an undocumented immigrant on April 11, 2018 in the Brooklyn borough of New York City. New York is considered a "sanctuary city" for undocumented immigrants, and ICE receives little or no cooperation from local law enforcement. ICE said that officers arrested 225 people for violation of immigration laws during the 6-day operation, the largest in New York City in recent years. (Photo by John Moore/Getty Images)

Angelina Godoy started digging for answers more than a year ago.

The human rights researcher had heard that ICE agents occasionally swept up migrant kids and locked them up in juvenile detention facilities, but she had no idea why.

One of the places ICE supposedly housed these young people, Godoy learned, was a few hours from her home in Seattle. She searched online for information about the detentions, but couldn't find anything that explained what was going on. She then filed a series of public records requests with officials at the juvenile detention center closest to her, hoping they could shed light on what ICE was doing and why these minors were being held in places run more like jails than the shelters most migrant children end up in when they are detained. She had specifically requested detailed detainee files, with names and personal information redacted, and the facility was ready to share them with her.

© Corinne Thrash/University of Washington College of Arts & Sciences Angelina Godoy is still seeking documents about ICE's detention of minors.

But what happened next stunned her: ICE blocked the facility from sharing the records and the federal government even went to court to keep the information secret.

Unbeknownst to Godoy, she had stumbled upon an obscure pocket of the immigration system, where little is known, and little is divulged.

For more than a decade, ICE has been taking a small number of immigrant teens it deems to be dangerous far from their families and detaining them for months at a time.

© Kelly Burkhardt Photography Attorney Mary Chicorelli

For immigration attorneys and human rights experts such as Godoy, the practice is alarming.

"I may not object to the fact they are being held," said Godoy, director of the Center for Human Rights at the University of Washington. "But I object to the fact that nobody can even know who they are (and) why."

Public attention has primarily focused on the treatment of children who recently crossed the border illegally on their own or with their parents. These kids are usually held in Border Patrol camps, family shelters overseen by ICE or on their own in facilities run by the Office of Refugee Resettlement (ORR) for so-called "unaccompanied" children, after arriving without any parents or being separated from them.

But teenagers who are already living inside the country with a parent can be classified as accompanied. This means if they are apprehended by ICE, they can be put in secure facilities where ICE has contracted to hold them, mixed among other US youth. Attorneys said most cases they had seen involved undocumented children who had faced a criminal conviction, charge or accusation, but that ICE also has the authority to detain those legally in the country with visas and even green card holders if their criminal records place them in violation of immigration laws.

Related: Medical care in immigrant detention centers under fire

Immigrant youth -- regardless of their residency status -- are supposed to receive a number of legal protections when detained. Yet more than a dozen immigration attorneys describe the agency's detention of minors as a black hole with little oversight or easy access to lawyers who can help them navigate complicated immigration law.

The places these youth are held don't appear on ICE's online map of detention centers. The agency doesn't make its reports about the conditions of the facilities available like it does for others. And family members can't find their loved ones using the federal government's official detainee locator since it only provides information on adults.

"ICE juvenile jails are secret and unaccountable," said Heidi Altman, director of policy at the National Immigrant Justice Center. "And ICE wants it to stay that way."

ICE said it follows all rules about when a juvenile can be detained in a secure environment, and described the youth it holds as those with serious criminal histories, saying that "it would be irresponsible and potentially dangerous for the agency to allow these individuals to remain out of custody with a guardian," as they await immigration proceedings or deportation. It did not, however, elaborate on the specific allegations and evidence ICE has used to take them from their families.

***

Philadelphia attorney Mary Chicorelli remembers an immigrant mother who was "beside herself" after her son was taken from where they lived in North Carolina to a private juvenile detention center in rural Pennsylvania in 2017.

Immigration documents show the 16-year-old was turned over to ICE and sent to the facility after being arrested by local authorities over misdemeanor charges for marijuana and gun possession. Chicorelli recalled the teen looking even younger than he was and said he was free of any previous criminal record. She said he repeatedly asked when he would be able to see his mom again.

"The separation between the respondent and his mother has increased the stress and anxiety given his mother's health," Chicorelli wrote in a motion for his release, saying that the mother, a cancer patient, had brought her son to the United States to escape the violence in Honduras.

An immigration judge released him after Chicorelli emphasized in court filings that the teen hadn't been convicted of any of the criminal allegations since the charges were still pending. She stopped representing him after his release and was unable to connect with the family to find out what had happened to him since.

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Another North Carolina mother named Leticia, who has gone through immigration proceedings to obtain a visa and only gave permission to use her first name, said that after her 17-year-old son Victor was arrested by police last year, he warned her that ICE agents said they would be picking him up from a Raleigh jail. But she had no idea where they were taking him and no way of finding out.

She said as the weeks dragged on, she became increasingly frantic. She depended on Victor, whom she said she brought to the United States from Mexico when he was five. As her oldest son, he cared for her younger children while she worked long hours. He also supported the family financially by picking up odd jobs and working at McDonald's, where the manager described him as "responsible," "reliable" and "eager to learn," according to a letter shared by his attorney.

But his mother knew Victor had struggled. In a statement he later wrote for his immigration case, Victor, who did not feel comfortable using his full name but agreed to share documentation of his case, said he had a troubled childhood and suffered from depression when his dad left the family. Law enforcement and immigration records show he was convicted of breaking and entering and larceny for a string of car break-ins. He was also convicted of threatening a friend he claimed stole from him. According to a police report, Victor was waiting for the friend when he got off the school bus, took out some sort of knife -- which Victor told his attorney was a pocketknife -- and said "give me back my s*** or you're going to regret it." No one appeared to be hurt in the incident.

It was after receiving a suspended sentence and probation for his latest car break-ins, meaning he was ready to be released by local authorities, that Victor was taken into ICE custody last year. His mom said she worried about whether her son was okay and feared he would be deported back to a country he barely knew. She anxiously tried to find him, she said, asking ICE for information and searching the agency's online locator where family members can track the whereabouts of immigrant detainees. But his name was nowhere to be found.

"I didn't know anything," she told CNN in Spanish in an interview in July. The Seattle Times later published a story about ICE's use of Pacific Northwest facilities which included Victor's account. "I was afraid he might already be in Mexico."

She said she finally learned of his location when Victor called her from a juvenile detention facility in Oregon and told her not to worry about him. In a statement, the facility said parents are typically notified of their child's arrival within 48 hours, but that it could not speak to whether -- or how soon -- contact is made before a kid arrives at the facility.

According to his mother, Victor spent more than three months detained by ICE in Oregon.

Statements in Victor's immigration file from detention officers at the Oregon facility described him as respectful and a "model youth" -- saying he had integrity and helped to calm down and mentor other "more troubled youths."

He was facing deportation, but to prevent that from going on his record, he requested "voluntary departure" from the immigration court instead -- and his attorney said he was sent back to Mexico when he turned 18.

***

Government data reviewed by CNN shows that ICE has most recently been authorized to hold minors for longer than 72 hours at three juvenile detention facilities: the Cowlitz County Youth Services Center in Washington state, Abraxas Academy in Pennsylvania, run by private prison operator GEO Group, and the Northern Oregon Regional Correctional Facility's juvenile division (NORCOR).

According to data previously released by ICE through a public records request from a group of immigrant advocacy groups, there have been more than 130 bookings of minors by ICE for more than 72 hours between January 2009 and May 2017 -- a small fraction of the overall number of children detained by the government. The data also shows how some minors were held for hundreds of days, and one for more than a year and a half. It did not specify the circumstances of why the youth were being held. ICE told CNN in July that eight male teenagers were currently being detained but did not say how many have been in its custody since 2017.

Related: CNN investigation exposes preventable deaths and dangerous care in jails and prisons

A high-profile court settlement from 1997, known as the Flores agreement, dictates how immigrant children should be treated while detained. Among a number of protections, children are supposed to be released to known family members "without unnecessary delay." And more restrictive "secure" detention is typically meant to be reserved for those considered to be dangerous to themselves or others.

An ICE protocol manual filed in court last year lays out rules for who can be held in secure detention under Flores, stating that this group includes those who the agency determines are "delinquent" or "chargeable as delinquent" after facing a criminal conviction or accusation. But attorneys who have represented some of these teens say these rules can be left open to interpretation, and that ICE has been able to lock up teens facing a range of charges or accusations the agency views as "chargeable" offenses. The lawyers say that fights with classmates or photos on social media that allegedly suggest a gang affiliation have been used as part of the rationale to detain certain teens.

CNN reviewed immigration documents from three separate cases. Two involved teens who had faced weapon possession charges, though they hadn't been charged with violent offenses. The third was Victor.

Unlike these youths held in juvenile detention facilities, so-called "unaccompanied" migrant kids taken into custody, often while crossing the border, are sent to facilities run by the Office of Refugee Resettlement. They receive access to legal services through a network of government-funded attorneys who are given lists of children detained by ORR. These attorneys visit the facilities, brief the children on their rights and help them find legal representation.

ICE said juveniles in its facilities should have legal access as well, saying that youth "are advised of the pro bono attorney lists that are posted within facilities" and that staffers can help them call lawyers.

Related: He applied for a green card. Then the FBI came calling

But without a more structured program in place for kids in ICE custody, attorneys and immigrant rights advocates say that it is far harder to make sure every kid actually obtains representation -- making a lack of legal access one of their biggest concerns about the practice.

The same attorneys notified about every kid in ORR detention aren't given a list of those in ICE detention. So even if they wish to help the children for free, they say it's difficult for them to learn who these teens are.

The National Immigrant Justice Center's Altman said that as a result, ICE is able to levy serious allegations of gang affiliation and other unlawful conduct -- and children are left "hard pressed to defend themselves."

***

At least two of the three juvenile detention facilities used by ICE have been accused of mistreating kids in the past. Abraxas Academy, in Morgantown, Pennsylvania, has been cited by state regulators for alleged sexual harassment and sexual abuse, as well as excessive use of force to restrain children. In 2015, one staffer who was later fired bit a child, and in 2016 other employees put kids in headlocks, according to the state inspection reports. The facility did not comment directly about the findings in these state inspections, but said its mission is to "provide safe and humane care" and that the contract to hold ICE juveniles expired in June, with the last teen released in August.

The NORCOR juvenile detention center, meanwhile, was the subject of a 2017 report from Disability Rights Oregon, a nonprofit that under federal law has the authority to investigate certain facilities in the state. The report highlighted "inhumane conditions" at NORCOR -- saying "conditions were harsher and more restrictive than any adult jail we had visited."

Related: 19 years old, in jail and begging to go to the hospital

NORCOR said it disputed many of the findings in the report but acknowledged that a review of policies and practices was necessary. After changes were made, NORCOR said an independent review found the facility was "safe, open and hospitable." It also said it encourages families to remain connected to the youth held there, making visitation available five days a week and allowing teens two free phone calls each week.

The third location used by ICE for juveniles, the Cowlitz County Youth Services Center, said ICE would need to comment about the reasons teens are sent there. It also said that kids with attorneys are allowed to have contact with them and that employees notify parents of their child's whereabouts as soon as they receive contact information from ICE.

***

Godoy, the human rights researcher set on finding out more about this practice in the Pacific Northwest, said one of the aspects that disturbs her most is that even if a court has adjudicated a case and determined a teen can be released to the public, ICE is able to step in and detain them longer.

She said this opens the door for potential abuses of power -- especially given the lack of transparency surrounding ICE's justification for locking these teens up instead of allowing them to go through immigration court while home with their families.

Godoy is now involved in time-consuming, complicated litigation as the federal government has fought to keep the documents she wants from being released.

The agency is arguing that the county cannot release them without violating a federal regulation preventing state or local governments from making these kinds of detainee records public. But Godoy still questions this reasoning and why the agency is so set on keeping her from the information.

"The level of aggressiveness with which they are pursuing secrecy should alarm us," she said.

What should we investigate next? Email us: watchdog@cnn.com.