Some migrants arrested in Trump’s immigration crackdown have been released back into U.S.

The Trump administration aggressively publicized the arrests of more than 8,000 immigrants by federal agents since Inauguration Day, with the promise that those detained would be part of a historic mass deportation. But NBC News has learned that some have already been released back into the United States on a monitoring program, according to five sources familiar with the operations.

Arresting more people inside the United States on allegations of immigration violations means they need to be held somewhere. And significant space constraints in Immigration and Customs Enforcement detention facilities — and federal court orders forbidding indefinite detention — have forced the agency to release some of those arrested in the roundups rather than hold them until deportation.

ICE posts arrest figures daily on X, but it does not disclose how many of those arrested are released, remain in detention or have been deported.

In a statement to NBC News, an ICE spokesperson acknowledged federal court cases limit ICE from detaining people indefinitely if their countries refuse to take them back, which can lead ICE to release them.

Those released are being kept on a monitoring program known as Alternatives to Detention, the five sources familiar with the releases said, which has for more than a decade been used to keep track of where migrants are as they make their way through the immigration system. ICE can track them by ankle monitors or wrist bands or through telephonic check-ins.

Trump’s ban on “catch and release” appears to be in effect at the southern border, where few migrants are being processed for asylum claims. But because ICE is funded for only 41,500 beds nationwide, it is still releasing some migrants who were detained in the interior of the country.