That could not have been a gasoline and rags arson, IMO.
Maybe employees were cooking crack or meth in the back?
Employees don't reset the alarm unless they either KNOW there isn't a fire or they were covering up some chemical operation and they thought they had it under control.
Nobody is going to risk losing their place of employment unless they're covering up something they don't want the bosses, and the police, to know about.
I just talked to a firefighter who was on the scene. Evidently the roof was being refurbished and it was the first to catch on fire. This is probably why the staff didn't notice the fire inside the structure.
The burning roof eventually collapsed on top of offices and the warehouse which was full of wooden racks, partitions etc and the whole place got incinerated.
My partner lost two years worth of wine and he's pretty devastated. His whole effort got smoked.