The fire department has issued several code violations against the building owner.
The third death going back about 9 months, of an elderly woman who lived in the same unit is being investigated.
She died at the hospital but they are looking at the history of her case to determine the cause.
The rest of the residents cleared out of the building on Baldwin Avenue Tuesday night.
Paramedics had to attend to the mother of Rosario Ferreras-Matos Tuesday night because the anguish was too deep and too great to bear.
"She was taking care of herself, she bought her car, like every other person does, and it's so hard, so hard," said German Ferreras, the victim's brother.
24-year-old Rosario Ferreras-Matos moved away from her parents Monday. It was a huge first step towards independence.
She didn't know that an unopened box of carbon monoxide detectors sat in her landlord's basement.
That landlord, Farouk Todrous had not installed CO2 alarms in any of his apartments.
Tuesday night he insisted, "Everything is OK, everything is OK. There's no gas leak no nothing."
The tough questions like, "Why didn't you have smoke detectors and carbon monoxide detectors?" he refused to answer, and ran away from reporters.
"He had blood on his hands, absolutely no question. Had he installed those carbon monoxide detectors once again, those people might have been alive, or at least this young woman here," said Armando Roman, the Jersey City Fire Director.
"This is an irresponsible person by renting this place, you know I can't believe, I'm still in shock, I can't believe that my sister is dead. We can't believe it, we can't believe it," Ferreras said.