Cellars are a common place to store computer servers - perhaps they are guessing that they are stored down there and are rendering them in-operable and therefore taking out the electronic brains of the company and security equipments to allow easy access. Watch out for men dressed in dark blue boiler suites carrying tool boxes and small ladders. If you have metal detectors make sure the tool boxes are inspected for secret compartments at the bottom concealing the silenced pistol.