Smoke coming out of the air vents?

I was in class and there are buildings and we were in the computer lab and it started smelling like metal or like something electronic was burning so we were all looking and we looked up and thick grey smoke started filling the room like really quick and we all ran out and like 5 fire trucks came and only blocked... show more I was in class and there are buildings and we were in the computer lab and it started smelling like metal or like something electronic was burning so we were all looking and we looked up and thick grey smoke started filling the room like really quick and we all ran out and like 5 fire trucks came and only blocked off the building I was in. Everyone is curious to what could have caused this, does anyone know? thank you
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