The couple bringing the suit is clearly setting the blame for the fire itself at the feet of the production company, and then also blaming them for not handling the fire properly once it happened.
The lawsuits were essentially inevitable following the fire, which, in addition to destroying the building, took the life of firefighter Michael Davidson who attempted to help put out the blaze.
As of this point, there has been no determination made of exactly what caused the fire, at least nothing that has been released publicly.
We can likely expect a series of lawsuits to follow this one from other tenants, whoever owned the building, or anybody else who feels the fire has damaged them in any way.