Tucson, Arizona - The FBI has doubled the reward for information about the kidnapping of NBC host Savannah Guthrie's mom after a person of interest in the case was briefly detained and then released.

The agency is offering up to $100,000 for tips about 84-year-old Nancy Guthrie's whereabouts or those responsible for her disappearance. The previous reward had been set at $50,000.

Guthrie has been missing for nearly two weeks. Investigators are treating the case as a suspected kidnapping and are searching for a male suspect described as between 5 foot 9 and 5 foot 10, with an average build.

The updated description follows a review of surveillance footage showing a masked individual at the front door of Guthrie's home near Tucson. The man was carrying a black backpack, according to the FBI.

A black glove, which will be tested by forensic teams, was also discovered inside the residence.

Savannah Guthrie and her two siblings have issued repeated video appeals in recent days to the unidentified suspected abductors following multiple letters, saying they were willing to pay ransom for the return of Nancy.

Authorities on Wednesday also detained but later released a person of interest in the case.