When he landed in Michigan in late May, all the little boy carried was a trash bag stuffed with dirty clothes from his dayslong trek across Mexico, and two small pieces of paper — one a stick-figure drawing of his family from Honduras, the other a sketch of his father, who had been arrested and led away after they arrived at the United States border in El Paso, Texas.

An American government escort handed over the 5-year-old child, identified on his travel documents as José, to the American woman whose family was entrusted with caring for him. He refused to take her hand. He did not cry. He was silent on the ride «home.»

The first few nights, he cried himself to sleep. Then it turned into «just moaning and moaning,» said Janice, his foster mother. He recently slept through the night for the first time, though he still insists on tucking the family pictures under his pillow.

José’s separation from his father is part of the United States’ most widely debated border enforcement policy. Last month, Attorney General Jeff Sessions announced the government would criminally prosecute anyone who crossed the border illegally, a directive that is leading to the breakup of hundreds of migrant families and channeling children into shelters and foster homes across the country.

In just the first two weeks under President Donald J. Trump’s new policy, 638 parents who arrived with 658 children had been prosecuted, administration officials told Congress.

Kirstjen Nielsen, the homeland security secretary, said separating families was not the aim but merely the effect of its new approach. «We do not have a policy to separate children from their parents,» she told a Senate committee. «Our policy is, if you break the law, we will prosecute you.»

The policy is creating heartbreak and trauma for those subjected to it, with parents and children often unaware of one another’s whereabouts.

KIND, an organization that provides minors with legal counsel, says it is aware of at least six children left behind after their parents were deported, including a 2-year-old girl.

José’s last name and that of his foster family, as well as where they live, are not being published in order to protect their privacy. Since his arrival in Michigan, family members said, a day has not gone by when the boy has failed to ask in Spanish, «When will I see my papá?»

They tell him the truth. They do not know. No one knows.

«I am watching history happen before my eyes,» said Janice, 53. «It’s horrendous.»

Janice, her husband, Chris, and their two teenage daughters are among a number of families who have in recent years provided a temporary home to minors seeking refuge in the United States.

In the last two years, 12 children have occupied the room upstairs. All had arrived in the United States alone and remained in the family’s care until a long-term sponsor already in the country, often a relative, was identified.

«They had access to their parents on a daily basis,» Janice said. «They talked to them on the phone. We have done video chats with Mom and Dad and siblings with every placement — except now.»

José is the first child they have hosted who crossed the border with a parent, then was forcibly separated. On his flight to Michigan were two other Central American boys in similar circumstances.

Bethany Christian Services is coordinating foster placements for about 100 migrant children, including José.

Among other children recently fostered by Bethany families is an 18-month-old girl separated from her father, who has been detained. The child cries frequently.

A 3-year-old boy taken from his mother at the border was inconsolable during his flight to Michigan and cried incessantly on arrival at his new home last month, said Dona Abbott, Bethany’s refugee program director. He recently has begun to bond with his foster mother, from whom he is now reluctant to be apart. «He seems fearful of losing yet another attachment,» Ms. Abbott said.

At first, José was sad and withdrawn.

He refused to shed the clothes he had arrived in, an oversize yellow T-shirt, navy blue sweatpants and a gray fleece pullover probably given to him by the authorities who processed him in Texas.

«I realized that he didn’t want anyone to take anything away from him,» Janice said.

The one thing that animated him was discussing his «photos,» as he called the family drawings.

He introduced «mi familia,» pointing to the figures of his parents, brother and younger sister. Staring intensely at the sketch of his father, with a slight mustache and a cap, he repeated his name out loud again and again.

It was «just me and him» on the trip from Honduras, he told Janice one night as he lay in bed shuffling the pictures.

The boy has begun attending a multi-age kindergarten at Bethany with a handful of other migrant children.

By the beginning of week two with the family, he cracked some smiles and even allowed himself a few giggles.

«It’s incredibly conflicting for me as a parent to watch this little boy begin to just have fun and experience joy in simple pleasures,» Janice said. «His dad doesn’t get to see him being joyful. It’s as if these moments with his son have been stolen from him. I am no substitute.»

Earlier this month, José finally spoke with his parents. The phone calls were separate: His father remains in detention, and his mother is in Honduras.

The calls changed everything. «It triggered all the separation trauma again,» Janice said.

She tried to offer him his toys, but he screamed and cried at the kitchen table for almost an hour.

When his fury subsided, the boy collapsed on the kitchen floor, still sobbing. «Mamá, Papá,» he said, over and over.

Nearby lay the family pictures, which he had flung on the floor.

Arrest and separation awaits families at the American border.