Some ransom notes sent in Nancy Guthrie case still being investigated as legitimate, FBI says

The FBI has discounted some of the ransom notes that surfaced after the disappearance of Nancy Guthrie as nothing more than extortion attempts, but the agency said Wednesday it's still evaluating others that might be legitimate.

The FBI did not specify how many ransom notes have been received, other than saying "several."

READ MORE: After reports of ransom note, Savannah Guthrie begs public for tips about her missing mother

"This case continues to be investigated as a kidnapping for ransom case," the FBI said in a statement.

The Pima County Sheriff's Department is also investigating the case. The department declined to comment on the notes Wednesday but said it's taking every tip in the investigation seriously.

Tucson TV station KOLD has said it received two notes, one demanding millions in Bitcoin in exchange for Guthrie's return and another that said she had died. TMZ also received a note.

READ MORE: Police in Nancy Guthrie's case might turn to genealogy databases to search DNA evidence

Guthrie is the mother of longtime "Today" show host Savannah Guthrie. Authorities believe she was kidnapped, abducted or otherwise taken against her will on Feb. 1. They found blood near the front doorstep of her home just outside Tucson, and the FBI later released surveillance videos showing a masked man on the porch that night.

Volunteers and search teams scoured the nearby desert terrain filled with cactuses, bushes and boulders in the weeks after she vanished. A volunteer group recently conducted a search for her body near the Arizona-Mexico border.