Well, if it was a legitimate enterprise, to jack up the perception, it would be called a "pharmaceutical plant".
If it was pumping out illegal and/or fraudulent drugs, then "chemical factory" would be do for a cover that would explain inflow of chemicals.
Looks like the company descriptions are quickly being scrubbed from the net.
They were listed as a producer of various forms of Phenylene-DiAmine. That’s a chemical commonly used in many industries as a polymerization inhibitor... ie, a chemical that prevents fouling in other processes.
Generally, not all that hazardous, but... has a LOT of potential energy in the molecule.
From the looks of the damage, this was almost certainly a BLEVE (Boiling Liquid Vaporization Explosion). They power in such an event is incredible.