Investigators say two men died after using a generator inside a warehouse. One man has been identified as Andre Benoit, 55, of Fresno. The other is Michael McCloskey, also of Fresno.
A female victim remains in critical condition at Community Regional Medical Center.
The owner of the business called 9-1-1 when he found the men dead, and the woman struggling to breathe.
Fire crews say she was likely poisoned while trying to help the men.