PASSAIC (AP) -- Carbon monoxide killed two people in a recording studio at a converted factory building and sickened a dozen others, authorities said.

An industrial building in Passaic where 2 were killed by carbon monoxide (CBS New York)

Passaic Mayor Alex Blanco said at a news conference that police responded to a 911 call at about 1:30 p.m. Saturday from Streets Rehearsal Studio and found the two dead on the second floor of the three-story building. The other 12 victims "experienced confusion and were choking" as they tried to leave the mixed-use commercial building, he said. They are being treated at local hospitals. The identities of the victims were not released until family members could be notified.

The music rehearsal studio in which the two were found dead is one of several in the building in Passaic, a blue-collar city about 15 miles west of New York.

"This is a sad day for the city of Passaic," the mayor said.

The cause of the carbon monoxide poisoning is under investigation by the county prosecutor's office.

A city spokesman said hazmat teams, fire departments, ambulances and a gas company were on the scene and responders from neighboring towns helped bring victims to three hospitals.

"If it wasn't for their quickness, there'd be more fatalities," Blanco said.

Keith Furlong, the spokesman for the city of Passaic, told The Record newspaper that mixed-use commercial buildings are not required to have carbon monoxide detectors.

The studio's website says it opened in 1994, offers 300-400 square foot studios that offer "the serious musician a secure sanctuary in which to hone their craft."

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