We heard from David Cruz, communications director at the League of United Latin American Citizens.
He told Sky News that people in Los Angeles received what he described as "false invitations" for an immigration hearing at the federal building.
But, since then, they were "never seen again".
He said: "What was more concerning were the false invitations that were being sent out to immigrants, some of whom had been here more than 10 years.
"They arrived at their immigration hearing at the federal building in downtown Los Angeles, never to be seen again.
"We found out about it 72 hours later when 200 detainees were being shipped to points unknown around the nation and beyond.
"That's what this reaction from our community."
Sky News has approached ICE for comment.