An operation to arrest thousands of undocumented immigrant families in several cities across the US is expected to begin Sunday, and one of the largest family detention centers has stopped booking new detainees to clear space to hold them, according to two sources with knowledge of the plans.

The planned multiday operation will target undocumented families who have been issued final removal orders, and comes soon after the administration secured additional funding to handle the record number of families crossing the border this year.

Meanwhile, the South Texas Family Residential Center in Dilley, Texas, has stopped admitting new detainees, dropping its population from 1,628 people to just over 200 as of this week and creating added capacity to hold families picked up in the raids. Families generally cannot be held for longer than three weeks.



A similar operation was canceled last month. President Trump claimed the move was a way to continue negotiations with Democrats, while others in the administration blamed leaks of operational details. Since then, US Immigration and Customs Enforcement has undergone major changes, with former acting director Mark Morgan shifting to lead US Customs and Border Protection and previous leader Matt Albence returning to head up ICE.

The raid suddenly canceled last month included the potential for separations of families in situations in which officers had concerns about the safety of the children, according to a source with knowledge of the operation.

Extensive training or guidance, however, was not issued to officers in the field and there had been no plans to coordinate with child welfare experts or advocates, according to the source.

The forthcoming operation will be "traumatic" for children who were members of the targeted families, the source said. "Including child welfare experts or social workers would ensure the best interests of the child are considered," the person said, adding that such coordination could help in "complicated situations or when making housing or other determinations."

The target list included individuals in the family case management program, an Obama-era plan that kept certain families together and provided them with a case worker, who had final removal orders. The program, which the Trump administration ended in 2017, was a particular target of many within the agency who were frustrated by the effort.

In the past several weeks, attorneys and civil rights organizations have distributed notices that they are prepared to help immigrants caught up in any operation. They also reminded people that they are not legally required to open the door to ICE officers.

Other advocates have signed up volunteers to film ICE officers if operations are reported by community members.

“We don’t want them to panic or give into this fear the current administration is trying to instill into our communities. We are ensuring they have the tools necessary if something were to happen,” said Ariana Martinez Lott, coordinator of the Faith In the Valley Watch Network in Northern California.