@tanguatlay,
Let's simplify the sentence:
1. Authorities said the worst was yet to come.
2. Authorities said the worst had yet to come.
I think #1 sounds more natural but I believe they are both correct.
And an aside, from Shakespeare's
King Lear:
Quote:“And worse I may be yet: the worst is not
So long as we can say 'This is the worst.”