The state medical examiner's office says one of the firefighters died of smoke inhalation, while further study is needed on the second firefighter.
The medical examiner's office says 49-year-old Michel Baik died of smoke inhalation. The office says he also had coronary artery disease that contributed to his death.
An autopsy was also done on 40-year-old Steven Velasquez, but it will require more study.
Velasquez and Baik were searching for people in need of rescue and ventilating the house when they sent out mayday calls Saturday, officials said. They were found unconscious.
The fire department has not had problems with its breathing equipment, which is checked daily when firefighters come on duty, Capt. Edward McCann said.
The air tanks give a warning of about five minutes when they are getting low, he said, but firefighters can become disoriented or have their exit blocked by fire, smoke or falling debris.