The FBI has unveiled new information about the suspect linked to the abduction of Nancy Guthrie, the 84-year-old mother of well-known US television personality Savannah Guthrie.

The agency has also announced an increased reward offer of up to $100,000 for any details leading to the discovery of Nancy Guthrie, or the arrest and conviction of those responsible for her disappearance.

Fresh details about the suspect, along with information about a black backpack, emerged following a forensic review of doorbell camera footage that captured an individual at Guthrie’s Tucson, Arizona home on the night she vanished.

According to a social media update from the FBI’s Phoenix office, “The suspect is believed to be a male, standing approximately 5’9″ to 5’10″ tall, with an average build. In the footage, he is seen carrying a 25-litre ‘Ozark Trail Hiker Pack’ backpack.”

“We are hopeful that this updated description will help refine the public tips we are receiving,” the FBI stated.

Since February 1, the FBI has received 13,000 tips from the public regarding this case.

Earlier on Thursday (Friday AEDT) media focused on a  white tent erected by law enforcement agents at the home of Guthrie.

The FBI says it was part of a testing procedure to create nighttime conditions similar to the time of day the 84-year-old went missing, a law enforcement source familiar told CNN.

Once FBI specialists set up the tent to create a blackout environment, replica clothing and a backpack similar to what the suspect was believed to be wearing were examined through the lens of what a doorbell camera might see at night, the source said.

The source said examiners looked at the reflections of lighting against the items to ensure they were confident in their brand names.

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