Firefighters work to contain a blaze at Apple's Mesa, AZ former sapphire factory
Apple purchased the structure and then leased it to GTAT for sapphire glass production. The company failed to produce the glass needed and ultimately filed for bankruptcy protection while leaving Apple without the material it needed for watch and phone surfaces.
Apple took back the factory and has been planning on turning it into what it called a “global command center.”
Since the building currently isn't in use, it's unlikely anyone was inside. There isn't, however, any official word yet on whether or not the building really is empty.
Update: The fire is out and seems to have been limited to the solar panels on the building's roof. 12 people were evacuated from the building with no injuries reported. There isn't any word yet on the cause of the fire.
[Thanks to ABC15 for the heads up]