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.

Eswatini, a country of 1.2 million people bordering South Africa, is the latest nation to accept third-country deportees from the U.S. The Trump administration has sent hundreds of Venezuelans and others to Costa Rica, El Salvador and Panama, and deported eight men earlier this month to South Sudan, also an African country.