As Anna Virginia Balloussier explains for Brazilian daily Folha de S. Paulo, the unit in question was one of three tasked with cooling down the museum’s auditorium, which stood directly below a popular gallery housing the reconstructed skeleton of a Maxakalisaurus topai dinosaur. (Miraculously, fragments of the 44-foot fossil survived the fire and were subsequently recovered by rescuers.)

The trio of air conditioners failed to meet manufacturer recommendations regarding the use of separate circuit breakers and grounding devices, according to an Agence France-Press report. The Associated Press adds that the units received a stronger electrical current than they were made to conduct, creating a powder keg situation poised for disaster.

Although electrical expert Marco Antonio Zatta called the faulty air conditioning unit the “primary cause of the fire,” inadequate safety measures throughout the museum facilitated the inferno’s spread. As Folha de S. Paulo’s Balloussier reports, the building lacked hoses, water sprinklers and fire doors, leaving its defense to a paltry fleet of fire extinguishers ill-equipped to stop a blaze of such scale.

In total, the fire lasted around six hours. According to the AP, temperatures in the ground-floor auditorium where the flames originated reached more than 1,832 degrees Fahrenheit, destroying much of the evidence needed to pinpoint the fire’s exact cause. Still, Spain’s Agencia EFE reports, investigators were able to rule out arson, as well as an early theory that posited a paper hot-air balloon may have landed on the roof and caught fire, by examining surveillance footage, conducting chemical analysis and studying the charred remains of the once palatial building.

Severe budget cuts the museum faced before the tragedy emerged as a key point of contention in the aftermath of the blaze. Due to its limited funding, the AP reports, the National Museum only spent $4,000 on safety equipment between 2015 and 2017. In the days and months following the inferno, protestors have vocally criticized Brazil’s systemic under-funding and neglect of cultural institutions, which they say allowed for the priceless repository of Latin American cultural heritage to vanish overnight.

The fire broke out at around 7:30 p.m. local time on Sunday, September 2. As the fire raged throughout the night, scholars, soldiers and firefighters worked to salvage artifacts from the museum’s expansive archive of anthropological, zoological and ethnographic objects: Although some items—including a “few thousand” mollusk specimens—were successfully rescued, initial estimates placed losses at up to 90 percent of the Rio de Janeiro institution’s 20-million artifact collection.

Five months after the blaze, archaeologists, anthropologists and paleontologists tasked with sifting through the rubble announced they had recovered around 2,000 items. Amongst the most significant items rescued from the flames are the 11,500-year-old skull of Luzia, the oldest human ever found in the Americas, and the Bendegó meteorite, a 5.8-ton space rock discovered in the Brazilian state of Bahia in 1784.

Writing for the AP in February, Yesica Fisch added that rescuers also retrieved fragments of indigenous Brazilian arrows, a Peruvian vase and a pre-Hispanic funeral urn. The National Museum’s “Post-Fire Rescue” portal further highlights a second meteorite named after the municipality of Angra dos Reis, two karajás dolls, a semilunar ax from Maranhão, pink quartz, an amethyst and a black tourmaline crystal.