Firefighters evacuated the building because some people were vomiting and experiencing shortness of breath.
A hazmat crew was called to the building to investigate the odor. Investigators say the building had recently been re-tarred and the fumes made their way through the ventilation system.
"When they turned it on, the swamp cooler, the initial blast of air sucked the tar on the roof into the facility and the patients that right under the vent got a blast of air," said Stin Hale with the Fresno County Fire Department.
Two residents and one staff member were taken to Community Regional Medical Center, but they're all expected to be okay.