According to activists, the recent deadly fire at a Mexican migrant detention center that claimed the lives of at least 40 individuals has highlighted the extremely harsh conditions that migrants are subjected to while housed in these facilities.

The incident was captured on video and shared on Facebook by a local organization called Equipo De Rescate Cd Juárez, which provides aid during emergency situations.

The video revealed a distressing scene of people trapped behind locked doors, attempting to forcefully kick them open in a crowded detention center, as smoke rapidly filled the space. Meanwhile, guards could be seen pacing outside the facility.

“We’ve been working hard to limit this detention, because this is exactly the kind of thing that happens,” said Gretchen Kuhner, the director of the Mexico-based group Women in Migration.

“The Mexican government tries to call them other things, but people are detained there, under lock and key, and they cannot leave … I’ve been here for 25 years in Mexico, and we’ve been working on the sickening cases that we have,” she told NBC News.

Although she has not visited the Estancia Provisional de Ciudad Juárez where the tragic incident took place, Kuhner explains that other migrant detention centers are often created by repurposing immigration offices, and generally lack proper facilities.

The regulation of these centers is a challenge due to Mexico’s limited access to outside organizations, according to Rachel Schmidtke, a senior advocate for Latin America at Refugees International. These facilities are like “black boxes,” shrouded in secrecy, Schmidtke says.

Mexico’s Supreme Court declared on March 15 that some of the country’s laws governing immigration detention centers are unconstitutional. Kuhner considers this a triumph for organizations that have been working to close these centers since 2000, but notes that more work is needed to address overcrowding.

Anthony Gonzalez, a Venezuelan migrant who was recently detained at the facility where the fire occurred, reports that hundreds of people were housed there, even though the capacity was only supposed to be 60. Mexico’s President, Andrés Manuel López Obrador, claimed that the migrants started the fire, but some are disputing that version of events.

Migrants are stripped of their possessions upon entering these facilities, including their shoelaces.