If I recall correctly, liquid titanium is spontaneously combustible in air...
As a powder or in the form of metal shavings, titanium metal poses a significant fire hazard and, when heated in air, an explosion hazard. Water and carbon dioxide are ineffective for extinguishing a titanium fire; Class D dry powder agents must be used instead.
Hard to know. Could be just that sparks initiated a fire below the layer of titanium cladding and whatever insulation or substrate was used was in some way combustible. Doesn't look like any updates thus far as to the cause of the fire.