(CNN) Hundreds of migrant children forcibly separated from their parents were transferred thousands of miles away from the border, and some already have been placed in foster care, officials said.
After crossing from the south, some children were taken to facilities along the border, including a new temporary shelter in Tornillo, Texas, while others headed to facilities as far away as New York.
Locations are chosen for a variety of reasons, said a spokesman for the Department of Health and Human Services. They include space availability, accommodations, demographics of the children and proximity to potential sponsors.
"There's an effort to place them as closely as possible to where they're going to be eventually reunified with a sponsor or a family member," he said.
He added it is "pretty rare" someone would go to New York, for instance, only because of space. It would probably be because an immediate family member is in the New York facility, the spokesman explained.
Without a publicly accessible database to track children, lawyers and case workers are determining locations probably by pulling state licenses and going shelter by shelter to figure it out, the spokesman said.
"How they move through these systems is largely space available and resources," said David Thronson, Michigan State University law professor and co-founder of the Immigration Law Clinic.
President Donald Trump has reversed a policy that resulted in the separation of 2,300 children from their parents, but it's unclear if or how those children will be reunited with their parents.
HHS has more than 100 shelters in 17 states to house unaccompanied children. Some of those facilities already are helping children who were separated from their families.
Federal authorities have been tight-lipped about where exactly all the children are held, but here are a few states where they have been sent.
The Homestead Temporary Shelter for Unaccompanied Children in Florida is a former Job Corps site that has been used as a shelter for unaccompanied minors since 2014. Photos taken this week showed boys and girls at the shelter.
On Tuesday, Florida Gov. Rick Scott sent a letter to HHS Secretary Alex Azar expressing concern over "unconfirmed reports" that the shelter is "potentially holding children who have been forcibly removed from their families."
In his letter, Scott demanded confirmation of reports that children separated from their families were being sent to the Homestead shelter. He also requested information about health screening protocols at the border and what, if any, health and education resources were being provided to children placed in Florida.
Children as young as 3 months old have been transferred to facilities in Michigan, according to the state's Department of Civil Rights.
"We have received reports and are very concerned that the children arriving here are much younger than those who have been transported here in the past," said Agustin V. Arbulu, executive director of the Department of Civil Rights.
At least 81 children have arrived in Grand Rapids since April, CNN affiliate WXMI reported.
Dona Abbott, director of refugee and foster care programs with Bethany Christian Services, said the children are in temporary foster care homes and group placements across the state.
Arbulu called the separation of families a federal issue but said his department is monitoring the situation because it "has a duty to make sure their civil rights are protected."
"While we commend the work of resettlement agencies in Michigan attempting to serve these children with dignity and compassion, nothing can replace the love, sense of security and care of a parent," he said.
Hundreds of migrant children, including a 9-month-old, have been taken to New York since the practice of separating families began, Mayor Bill de Blasio said.
At least 239 children are in the care of the Cayuga Centers in Harlem, which runs day programs for them. Some are in foster care, and others could be with relatives.
De Blasio said some of the children have bed bugs, lice, chicken pox and other contagious diseases. Some are too young to communicate and need significant mental health services.
"And this is just one of the centers in New York City," de Blasio said.
It's unclear how many separated children are in the city.
New York Gov. Andrew Cuomo said his office is aware of more than 70 immigrant children in federal shelters in New York. Cuomo plans to sue "to protect the health and well-being of children" held in New York and elsewhere, he said in a statement.
Five migrant children have arrived in South Carolina since last month.
The children are ages 7 to 11, and most will be placed in foster care in the Columbia area, CNN affiliate WCIV reported.
"They don't understand what's happening, or why they have been separated from their parents," said Rebecca Gibson, a program coordinator for transitional foster care with Lutheran Services Carolinas. "The children don't know if they will be safe. They don't know where their parents are, and no one has given them any information."
Gibson said only one child has been released to a sponsor in the United States.
"We don't know the circumstances of how the separation happened, or if the children were able to say goodbye," she said.
Most infants and children are being held at new and old facilities in several cities, including McAllen, Tornillo and Brownsville, after they cross into the United States.
Some children under 13 are staying at newly built facilities such as a former private home about 20 miles from the US-Mexico border in the town of Combes, operated by Southwest Key Programs.
Democratic US Rep. Filemon Vela Jr. of Texas said he toured a new shelter in Brownsville, where about 40 children under 10 are staying.
One room held four infants, two of whom were accompanied by their teenage mothers, he said. The children receive constant attention, Vela said. "People are doing what they can under the circumstances."
One facility for the children is in Bristow, more than 30 miles from the nation's capital. Youth for Tomorrow, a nonprofit founded by former Washington Redskins coach Joe Gibbs, has been partially used as a shelter for unaccompanied minors for several years.
Photos released this week by HHS showed girls wearing uniforms sitting in an auditorium, a set of baby high chairs, a room with cribs and a woman carrying a baby.