A private prison in Kansas could soon be holding migrants as part of President Trump’s promise of mass deportations for those living in the U.S. illegally. (AP Video: Nick Imgram)

Migrants are being detained by immigration agents in courthouse hallways nationwide, sometimes moments after pleading their cases, raising alarm among attorneys and advocates who say the practice is turning immigration courts from places of due process into zones of fear.

Immigration attorneys tell ABC News that federal agents are arresting migrants at immigration courts -- in some cases after their deportation cases have been dismissed.

Nydia Velazquez, D-New York, went to 26 Federal Plaza, a Manhattan skyscraper housing immigration court and ICE offices where they believe migrants are being held. Agents kept them from inspecting ...

The ICE agents detained the migrants after they checked in at an office on Elk St. right across from City Hall.

A group of ICE agents and the migrants they're holding in Djibouti following an order by a U.S. federal judge are at grave risk, an immigration official says.

In a post on social media, Garcia accused top Trump aide Steven Miller of directing ICE to target minors in foster care in a “desperate” attempt to meet a “quota of deportations.” When asked by The Herald, she said she could provide specifics only about the Pensacola case.