The note also gave details that suggested the abductor had been at Nancy's home, sharing that the frail grandmother's white smartwatch was on the floor at the foot of the bed, and pointing out that a backyard floodlight had been destroyed.

At the time, the letters were sent to two local Tucson TV news stations, as well as TMZ.

NBC News reported on June 22 that a second note from the kidnappers claimed Nancy died shortly after she had been taken from her home.

TMZ claimed on February 13 that they received a third letter appearing to be from someone who could identify the kidnappers in exchange for money. Savannah and her family later offered a $1million reward for Nancy's recovery in late February, but it has not produced any leads.

While the FBI has not officially stated that the letters are fake, a bureau official told Reuters on June 30, "None of the ransom notes are believed to be genuine."

A second law enforcement source with knowledge of the case backed the FBI's conclusion that the ransom notes did not appear to be credible.

Nancy has been missing for nearly six months with no clues as to where she was taken and what her fate was. A Nest doorbell camera showed a masked man armed with a gun at her front door in the hour she went missing, but he was never identified by authorities.