Five immigrants deported by the United States to the small southern African nation of Eswatini under the Trump administration’s secretive third-country program are in prison, where they will be held in solitary confinement for an undetermined time.

The Trump administration sent five deportees to Eswatini, an African kingdom, saying that their own countries would not take them. But Eswatini says it will send them home.

The administration has made the practice of third country deportations central to its sweeping immigration policy.