What they have been trying to determine is the cause of death. They may know some underlying problem without making her medical history public.
If she had one of the two problems I mentioned, and they had been the sole cause of death, they wouldn’t be looking for another cause.
It would have been easier if they had pinned it on a health problem.
BTW, heart attacks take place more frequently around this time of day
Of course, if that had been the problem, the cause of death would have been rather evident.
Sounds like they're having enough trouble determining the cause of the fire.