FBI agents conducted a late-night search of Nancy Guthrie's septic tank as part of the ongoing investigation into her apparent kidnapping from her Tucson, Arizona home. The search comes one week after the 84-year-old mother of NBC's Savannah Guthrie was reportedly taken from her residence.

Investigators were seen removing a manhole cover at the back of a smaller building on Guthrie's property, the same location where FBI agents were spotted on the roof just days earlier. Despite the extensive search efforts, the Pima County Sheriff's Department reported no suspects, persons of interest, or vehicles have been identified in the case.

The suspected kidnappers have demanded a $6 million bitcoin payment by Monday evening, according to a note sent to a local TV station. Savannah Guthrie, flanked by her sister Annie and brother Camron, made a public plea to the kidnappers, begging for her mother's safe return so the family could celebrate together.

Quick Fact: The suspected kidnappers are demanding $6 million in bitcoin by Monday evening.