The fire authority didn't blame the car. Here's the quote from the article:
The Fire Authority, however, released a report stating that the fire occurred "as a result of an electrical failure in the charging system for an electric vehicle".
Fire broke out in the garage on the campus of the University of California-Irvine on November 15. The blaze was noted by the car's owner just before 3 am, and it was promptly extinguished by fire crews.
The incident caused up to $25,000 of damage, though the Model S itself sustained only light smoke damage. Nobody in the house was injured.
While the Fire Authority's report stated the most likely cause was a "high resistance connection at the wall socket or the Universal Mobile Connector from the Tesla charging system", Tesla says its own data shows the car was charging normally, with no fluctuations in the temperature and no malfunctions capable of causing a fire.
Tesla also notes that the car's charging cable was fine where it was connected to the car, and was damaged only on the wall side. This could suggest issues with the building's electrical supply, rather than with the vehicle.
This doesn't completely rule out the charging system. The fire was started between the wall socket and the charger.