Unsubstantiated

Meanwhile, another cruise ship, the Westerdam, finally docked Thursday in the Cambodian port of Sihanoukville, ending a two-week-long saga that saw the ship being turned away by Japan, Thailand, Taiwan and the Philippines due to unsubstantiated fears that someone on board had been infected.

That's an unsubstantiated claim.

These are unsubstantiated accusations.

It looks like you're writing unsubstantiated nonsense. Would you like to turn on all caps?

That rumor is unsubstantiated.

Certainty, it was an unsubstantiated rumour.

Obviously, it was an unsubstantiated rumour.

Such hedging is necessitated by the lack of in-depth knowledge of the contents, which also gives free rein to the scripting of unsubstantiated factoids concerning the book.