Families of Venezuelan deportees held in El Salvador’s infamous Cecot prison can petition the Salvadoran government for their release – but the fruitfulness of that process is an open question in a country accused of arbitrary detention by rights groups and even the US State Department.

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.

Over the weekend, the Trump administration deported hundreds of Venezuelan migrants to El Salvador, where they are being held in a maximum security mega-prison called the Center for the Confinement of Terrorism (CECOT).