The methodically planned strategy is intended to pressure noncitizens, including many with legal status, to leave the United States.

© Salwan Georges for The New York Times

Clashes between protesters and armed federal agents have erupted at the parking lot of Delaney Hall in Newark since the Memorial Day weekend.

© Todd Heisler/The New York Times

But details remained scant after officials said last week that, with “extraordinary” exceptions, people seeking permanent residency must first leave the country.

© Valerie Plesch for The New York Times

For nearly a week, relatives of migrants at Delaney Hall have said that some detainees have been on a hunger strike at the New Jersey facility.

© Andres Kudacki/Associated Press

Dong Guangping, 68, fled China at least three other times but was always sent back. His friends hope things might be different this time.