Exactly to what extent can APS conduct a financial investigation?

Can they go into the aged bank accounts which my sibling put his name upon?
(He controls my father?)
Can they check if CD:s have been transferred to his name?
Can they check if he has had my fathr sign beneficiary change forms?
I have seen blank beneficiary change forms around my dad's home.
Several hundreds of thousands of dollars are unaccounted for.
My mom and dad do not have enough for assisted living.
They are 91 and 67, in dementia, arthritic, but still basically healthy living
in their own home.
My brother, whom my dad has entrusted famly finances, claims most of all
monies are gone.
Called APS but has not heard nothing for months.
My brother has told geriatic doctor who called APS that this is all "imagined".
I am concerned my parents cannot deserve tot have the quality of care that they have worked and saved all their lives for.
My sister in law runs the show.
I have been excluded from all financial decisions.