For a month, Meybelin has lived in a massive convention center located in the heart of San Diego. There, along with hundreds of other migrant children, she waits day in and day out to be released to a relative in the United States, frequently calling her parents in El Salvador distraught about the prolonged wait. Meybelin, 17, is one of the more than 20,000 minors in the custody of the Department of Health and Human Services as a result of a record number of unaccompanied children and teenagers arriving at the US southern border this year. The Biden administration has scrambled to assist the department’s already-strained resources and are using a host of novel locations, like convention centers, to shelter minors. While the administration has made inroads in quickly transferring children out of jail-like Border Patrol facilities, it now faces another daunting challenge: reuniting an unprecedented number of children with family or guardians in the United States. In more than 80% of cases, children who cross the US-Mexico border alone have a family member in the US, according to the Department of Homeland Security. But getting them to those relatives is a timely and often arduous process. Officials have been grappling with the situation along the US-Mexico border and its ramifications since the early days of the administration, as an increasing number of migrants, particularly children, arrived. The administration faced swift criticism from both sides of the aisle for their handling of the border. Republicans seized on Biden’s immigration policies, arguing they’re encouraging migrants to journey north, while immigrant advocates slammed officials for continuing to rely on a Trump-era policy that allows the swift expulsion of single adults and families attempting to illegally cross the US southern border. On Thursday, Homeland Security Secretary Alejandro Mayorkas is testifying before the Senate Homeland Security Committee on the actions that have been taken to address the influx of minors at the US-Mexico border. For now, border arrests appear to have leveled off, but hurdles remain. Federal documents obtained by CNN reveal shortages in the number of case managers needed at six temporary facilities, including the San Diego site, for the number of children in care, as well as an ongoing need to continue building bed capacity for children. For the children, the reunification process can be dizzying. Meybelin’s case, according to her family’s attorney, has bounced around to different case managers, pushing back her release and raising concerns among her family and attorney who say she suffers trauma after being attacked in El Salvador. “What’s frustrating about this case is there’s a natural brother here, there’s an attorney who knows what they’re doing. But we’re getting a run around. You might expect that if you’re calling Amazon about a lost package, but this is a child,” said Kate Lincoln-Goldfinch, an immigration attorney based in Texas, referring to Meybelin’s older brother. Meybelin’s parents, Jose and Mirna, spent roughly three weeks fretting over the whereabouts of their 17-year-old daughter who had fled their home country of El Salvador to journey to the US after, they say, she was attacked and the family threatened. CNN is only using their first names due to privacy concerns. “It hurt,” Jose told CNN in Spanish, as he broke down crying. “My daughter is young. I don’t know if we’ll see her again.” Jose said he called the Office of Refugee Resettlement hotline every day, around the clock, to try to locate their daughter after she crossed the US-Mexico border. “We called every day. They said we could call 24 hours,” he said. Since Meybelin was transferred to the San Diego Convention Center, they’ve been able to connect almost weekly, but only for about 10 minutes at a time. The average time it takes to reunite a child with a sponsor is about 30 days, though officials are trying to shave off time. DHS is participating in an inter-agency task force focused on reuniting kids with their sponsors to identify what support they can lend, a senior Homeland Security official told CNN. Sponsors, like parents, relatives, or guardians, have to submit paperwork and undergo vetting. Case managers, meanwhile, gather a child’s details and help reunite him/her with a sponsor in the US. But in some cases, young children might arrive with little or no information to identify them. “[The reunification process] is extremely complicated and there have been other kids we meet with who didn’t come with any information about their families. In those cases, case managers have to act as detectives,” said Lindsay Toczylowski, an immigration attorney based in Los Angeles who’s primarily been working with children staying at the Long Beach convention center. Just this week, a baby found along the Texas-Mexico border with four other young girls had a phone number written down with a marker on her diaper. Once children are reunited with their sponsors, they still have to go through their immigration proceedings, which can take months, if not years. Many are seeking asylum in the US. But it’s ultimately up to an immigration judge to decide whether a child will remain in the US or be deported to their home country. Fleeing dangers in Latin America Dangerous conditions in Latin America are among the contributing factors for migration to the US. The region was also hit with two devastating hurricanes last year and continues to reel from the coronavirus pandemic, as Covid-19 cases and deaths have soared and economies once projected to grow have been decimated. In April, US Customs and Border Protection apprehended 17,171 unaccompanied children at the US-Mexico border, down from March but still higher than previous years, according to the latest available data from the agency. RELATED: Border encounters reach 2-decade high in April, though number of unaccompanied children dips Juana Cuyuch Brito’s 16-year-old sister crossed the US-Mexico border in early March after fleeing Guatemala because of the devastation left behind by last year’s hurricanes. Her sister, Lidia, was in Border Patrol custody for at least a week, until being transferred to HHS custody when they were finally able to talk over the phone, Cuyuch said. Her sister is now staying at an HHS shelter in Pennsylvania, still waiting to be released. One of the main challenges to reunifying kids with their sponsor is strained case management services, given the sheer number of children coming into custody. The consequence: children staying in shelters longer. Lincoln-Goldfinch is the co-founder of the non-profit Vecina, a family reunification project launched in conjunction with Project Lifeline to help parents and relatives get paperwork in motion in hopes of cutting down the time to reunify. “What these families have chosen to do is safer than the alternative and the wait, the lack of information, the lack of communication and the release delays is absolutely, excruciatingly painful for these families and these kids,” she said. Neha Desai, immigration director at the National Center for Youth Law, echoed those concerns: “Our team has spoken to numerous sponsors over the past few months and overwhelmingly, they have been terrified, confused and frustrated. Some of the sponsors had been waiting for weeks to hear from a case manager and had yet to receive a single call. Others had received an initial call, but no explanation of the steps in the process, clear expectations of the timeline, or reasons for the delays,” she said. Nathan Bult, senior vice president of public and government affairs for Bethany Christian Services, which works directly with unaccompanied children, underscored the role of case managers and the stress they’re under. “In Bethany’s programs, which are licensed by each state we’re in, our case managers have a caseload set by the license. The ratios are meant to keep them from getting overwhelmed. But they’re definitely stressed,” Bult added. More than 350 personnel from US Citizenship and Immigration Services, an agency under DHS, are helping with case management. The administration, officials told reporters last week, is improving some case management processes and updating policies to quickly unify children with their vetted sponsors. That includes implementing virtual case management, training additional case managers, and expediting the release of children to parents or guardians. The Office of Refugee Resettlement, an agency under HHS, says it’s also started to kick off the process of identifying parents or relatives who live in the US, while children are in CBP custody. In recent days, HHS has been discharging more than 500 children on a near-daily basis, according to government data, indicating progress as the number of children in the department’s custody declines.