Human rights advocates warn that the deportees legal rights were violated as they were transferred to the CECOT, a mega-prison established by El Salvador’s President Nayib Bukele for his crackdown on gangs in the country. The facility, according to the Associated Press, can hold up to 40,000 inmates; up to 70 people are housed in a single cell.

Families and lawyers fear for the deportees who may face indefinite detention in a prison known for human rights abuses.