Inside an immigration courthouse in the heart of Lower Manhattan, federal agents in T-shirts and caps cover their faces with masks as they discreetly attend routine hearings filled with immigrants.

The agents tip off other officers huddled in the court’s staid hallways as undocumented immigrants on their radar leave the hearings. They then move in to arrest their targets, sometimes leading to disorderly scenes as husbands are separated from wives, and parents from children.

The scene unfolding in New York City has repeated itself in immigration courthouses across the nation, a window into the Trump administration’s accelerating crackdown amid pressure from the White House to ramp up deportations. In Los Angeles, workplace raids have inflamed tensions and led to demonstrations. In New York, the courthouse arrests have emerged as a defining flashpoint.

In June, hundreds came and went at one federal building — for asylum hearings, citizenship applications and mandated check-ins with the Immigration and Customs Enforcement agency. Some left in handcuffs.

Immigrants arrested after appearing in courtrooms on higher floors were ferried by agents to holding cells on the 10th floor, an off-limits area where ICE typically keeps a few people for several hours as they are processed and transferred elsewhere.

But ICE agents have apprehended so many people showing up for routine appointments this month that the facilities appear to be overcrowded. Hundreds of migrants have slept on the floor or sitting upright, sometimes for days, said Francisco Castillo, a Dominican immigrant who was held there for three days last week.