Called for a possible structure fire, caller reported solar panels on the roof of the detached garage were on fire and might be spreading into the structure. Forest Fire C-8 arrived and started putting water on the roof to stop the fire from spreading into the structure. Tanker 16-5 arrived and checked inside the structure for extension, none found. Car 16-20 assumed command. Laddered the roof, found only one section of solar panel that had burned. Used CO2 extinguisher on the remainder of the fire. Removed the solar panel. Found an animal nest was under the panel and that the wires were chewed which likely caused the fire. Used 1-1/2\" hose line to clear out any debris or nests from under the panels. Notified state fire investigator and electric company.