“Panama cannot end up becoming a black hole for deported migrants,” said Juan Pappier, deputy director of Human Rights Watch in the Americas. “Migrants have the right to communicate with their families, to seek lawyers and Panama must guarantee transparency about the situation in which they find themselves.”

Migrants deported from the U.S. could be held in Costa Rica for up to six weeks before being sent to their home countries, Costa Rican President Rodrigo Chaves said on Wednesday.

Officials in Costa Rica and Panama are confiscating migrants' passports and cellphones, denying them access to legal services and moving them between remote outposts as they wrestle with the logistics of a suddenly reversed migration flow.

The migrants were flown from San Diego to San Jose, from where they were sent by bus to a migrant shelter near the border with Panama.