Nancy Guthrie, who was in frail health and had limited mobility, was last seen alive at her home on January 31.
The FBI announced Wednesday that it is investigating extortion demands related to Guthrie's disappearance. Federal authorities stated that some of the ransom notes received concerning the kidnapping were not legitimate.
The agency believes that two ransom notes reported in February, as well as a more recent message from someone claiming to know the identity of the alleged abductors, were fake communications and extortion attempts without legitimacy.
However, the FBI noted that other demands may potentially be legitimate and are still being investigated as such.