Hmmm. Very loud noise -- very loud; the floor trembled -- underneath the media room here. Apparently the zone below houses some mechanical devices to do with the Fleet Center train station (shut down a couple of days ago).
Cop sez: "It was something under the floor." Unhappy with this analysis, Matt is seeking further information. UPDATE: (Matt here) -- Basically, there's a big mechanical room under the press filing center, and, well, neither firemen nor cop could say just who is minding it. "Since no one else is complaining about it…." one fireman shrugged hopefully.