Junior College I went to in St. Pete about 45 years ago had a similar event happen in the science/chemistry building. I came in for classes only to find that section of the quad shut down, windows blown out of the first floor, glass everywhere. Turns out - as I was told by my chem lab professor - someone left a can of ether out where it vaporized over the weekend and, when the AC was turned on early Monday morning a spark from a relay or switch ignited the mixture. BOOM!
The absence of fire/smoke/soot is interesting, but some gas mixtures burn so quickly they utilize all the oxygen available for combustion and the pressure from the explosion blows out any small fires before they can propagate.
Sure that wasn’t Fight Club?