There can possibly be, several concurrent investigations, for different reasons.

Having 3 deaths, is one investigation.

The many condo/apartments that were destroyed, is another investigation.

The types of building materials that burned, is another investigation.

The comparison of other unrelated structure fires, to this fire, is another investigation.

The reviewing of the firefighting, resident evacuations, and the search & rescue (policies & procedures), is another investigation.

Etc...