Among the 2,000 undocumented immigrants being targeted now are those whose court cases were expedited, having typically missed a court date and been ordered deported from the country in absentia. They were sent letters in February demanding they report to an immigrations and customs office to leave the country, Mr. Morgan said.
While Mr. Morgan said the agency would still target violent criminals for removal, “priorities do not mean other categories are exempt.”
“And again,” he added, “I think family units are a good example of that.”
Homeland Security Department officials have changed their minds multiple times in recent days over when to start the operations. Officials have been nervous about creating scenes of armed agents pulling children from homes and the possibility that some families could be separated.
“It’s people, and people are complicated,” said Ronald D. Vitiello, the former acting director of the immigration and customs agency who had his nomination pulled by Mr. Trump after he warned of the bad impressions the raids would leave. “Some of them might be sick and need to be treated for illness. Some might be separated in a way that the child might be at school and the parents at home.”
More than 207,000 migrants have been released since December of last year, Mr. Morgan said. Many of them, he said, have taken advantage of laws that prevent the extended confinement of children, which enabled families to be quickly released after being apprehended.
“It’s clear if you grab a child that’s your passport in the United States,” Mr. Morgan said.
But the mass arrests come with logistical challenges.
There is limited space in the family detention facilities where migrants would be held while the government tries to secure their travel documents, which are required to deport them. But keeping families there could result in violations of the agreement, known as the Flores settlement, that established standards for the detention of children and limits it to 20 days.