— Carbon monoxide poisoning killed two people and injured 12 others Saturday afternoon at a Passaic music studio, according to the mayor. "It's a sad day for the city of Passaic," Mayor Alex Blanco said at a press conference outside the commercial building on Willet Street Saturday. The two individuals who died were in a room on the second floor of the multi-use commercial building, while the others were in separate rooms, Blanco said. The second floor of the building is comprised of a series of small recording studios, he said. Authorities have not yet released the names of the two people who died. A 911 call alerted authorities to the incident after the other dozen individuals began choking and acting confused, he said. Blanco said the fast response by first responders helped minimize the casualties. "If it wasn't for their quickness, there would be more fatalities tonight," the mayor said. Walt Schuwert, who works for the studios’ landlords, said there are about 20 studios part of the Streets Rehearsal Studios in the building. “It’s a tragedy,” said Schuwert. “It’s a loss life.” Musicians including My Chemical Romance have used the facility, he said. “A lot of people practiced here,” he added. “This is just a tragedy.” Officials said a dozen people were being treated at St. Mary's Hospital in Passaic, St. Joseph's Regional Medical Center in Paterson and Hackensack University Medical Center. Six of the patients were in stable condition at St. Mary's Hospital, according to hospital spokeswoman Vanessa Warner. The source of the carbon monoxide is currently under investigation, but the fire alarm system was operating at the time, Fire Chief Patrick Trentacost said. According to state regulations, carbon monoxide detectors are not required in mixed-use commercial buildings. Firefighters were gathered outside the building along with a hazardous materials team and investigators. Crews from Wallington, Lyndhurst, Moonachie and Clifton were among fire departments working at the building.

Naomi Nix and Noah Cohen of NJ Advance Media contributed to this report.

Justin Zaremba may be reached at jzaremba@njadvancemedia.com. Follow him on Twitter @JustinZarembaNJ. Find NJ.com on Facebook.