Immigrant rights activists gathered outside the Delaney Hall Detention Facility of ICE and held a vigil on Monday after a detainee, Edwin Lopez-Cornejo, 41, died in ICE custody in Newark.
The official cause of death remains pending further examination.
Lopez-Cornejo was apprehended by ICE on June 18 in Plainfield, New Jersey, following a prior removal from the U.S. in 2006.
He was being held at the Newark facility pending deportation.
The 41-year-old Salvadoran national died in federal custody after experiencing a medical emergency at Delaney Hall, the largest immigration detention facility in the New York metropolitan area.
Newark Mayor Ras Baraka issued a stinging rebuke following the incident, calling the death a "heartbreaking reminder" of a lack of oversight.
He accused the facility's operator, GEO Group, and ICE of showing a persistent "disregard for transparency" and public safety laws.
The death marks the second fatality at the facility since it opened a year and a half ago.
In May, detainees at the center launched a hunger strike to protest what they described as inhumane living conditions, vowing to "stop eating and stop working" indefinitely until conditions improved, and ultimately until they were freed.