A highly flammable foam was responsible for the death of 235 people in a nightclub in southern Brazil last weekend, filling the venue with a thick poisonous smoke within three minutes, police investigators say.
The toxic soundproofing foam, responsible for the illnesses of many survivors, may have been the Kiss club's greatest hazard, according to police in Santa Maria, who also faulted broken fire extinguishers and a single, obstructed exit for the tragedy.
"If it weren't for this material, no one would have died," said Santa Maria police chief Marcelo Arigony, holding a piece of foam, which was installed without a flame retardant coating.
"In parts of the club without the foam, almost nothing burned."
Police are investigating whether city officials were negligent in allowing the club to operate.
As part of a separate criminal investigation, police have also detained the club's owners and two members of the band, suspected by police of starting the blaze with a cheap flare.
Santa Maria's mayor and fire officials have traded blame for an irregular operating license and expired safety plan at the club.
The mayor has suspended the licenses of all the city's nightclubs and music venues for 30 days.
A nationwide crackdown on unsafe nightclubs also gathered steam, as Brazil's most populous state, Sao Paulo, and its capital city signed an agreement for the joint inspection of bars and clubs.
On Wednesday alone, authorities inspected 300 establishments in the state of Sao Paulo.
The hazardous foam used to dampen sound inside the Kiss club could claim more lives yet.
Many who escaped the blaze have since fallen sick from the toxic fumes they inhaled, putting 138 people in the hospital.
The number of victims in intensive care has also climbed to 87 patients on mechanical respirators.
Ingrid Goldani, a 21-year-old bartender at the nightclub, may have saved her life with a gasp of fresh air when she stuck her head inside a freezer before dashing for the exit.
But hours later, she fell ill at home and was taken to the hospital.
Doctors diagnosed her with chemical pneumonia, an inflammation of the lungs caused by inhaling poisonous gas. They warned it may be a week before other victims feel the symptoms.
Exams of some patients have shown airways coated in a thick black film, said Jaime Felipe Federbusch, a burn doctor who has treated victims at a hospital in nearby Porto Alegre.
"It looks like you're descending a chimney," he said.
The most serious injuries were not caused by direct burns, he added, but by the inhaled toxins such as cyanide that filled the club as soundproofing on the ceiling caught fire.
"That place became a gas chamber," said Federbusch.