Nancy Guthrie disappearance: vetting public tips is a large but vital task.

Authorities and the FBI have received tens of thousands of tips and calls after a porch-camera video of a masked person was released, and experts say vetting that information is an extensive but necessary task.

Nancy Guthrie was reported missing on Jan. 31 after a porch camera recorded a person on her property. Law enforcement released the video and asked the public for information. The FBI and the Pima County sheriff's office have reported receiving large numbers of tips and calls and have assigned several hundred investigators. Experts say reviewing and vetting those tips is time-consuming but important. Known details: - Nancy Guthrie, 84, was reported missing Jan. 31 and a porch camera recorded a masked person on her property. - The FBI and the Pima County sheriff's office say they have received large volumes of tips and calls and have staff working around the clock to review them. - Investigators and retired officials interviewed for the story say many tips will be irrelevant but public input has helped other investigations and cannot be ignored. Summary: The influx of public tips has created a substantial vetting operation for federal and local authorities, and officials describe tip screening as ongoing. Undetermined at this time.