The group, Cristosal, has investigated prison deaths and torture under President Nayib Bukele. Its employees were threatened and surveilled, its director said.

© Jose Cabezas/Reuters

© Adriana Zehbrauskas for The New York Times

In exchange for jailing more than 200 deportees, El Salvador’s president, Nayib Bukele, has become a favorite of the Trump administration.

© Eric Lee/The New York Times

In exchange for jailing more than 200 deportees, El Salvador’s president, Nayib Bukele, has become a favorite of the Trump administration.

© Eric Lee/The New York Times