LOS ANGELES, June 23 -- The mystery surrounding the disappearance of US television host Savannah Guthrie's mother has taken another chilling turn, with investigators reportedly examining a second ransom note that apologised for the 84-year-old's alleged death after her abduction.

According to the BBC, the letter was sent days after Nancy Guthrie disappeared from her home near Tucson, Arizona, in late January.

Unlike an earlier note demanding millions of dollars in bitcoin for her release, the second reportedly claimed her death had been accidental and included an apology addressed to her family.

US authorities have not publicly confirmed the contents of either note.

The Pima County Sheriff's Department declined to comment on the repor...