Mineral oil
They short the 120vac across the 12v dc bus and whala you have a fire.
Ya they use 12v for the computer and wireless communication. They must have remote capability to short the wiring 120vac requires 14guage wire at least 12v DC is 18guage. Running 120 vac over 18gauge immediately overheats and melts the wire producing you guess it a fire. They are shorting the 12v bus not 120 so nothing happens on the power companies side