The glove, discovered in a field beside a road, was sent for DNA testing. The FBI said in a statement it had received preliminary results and was awaiting official confirmation before investigators run the results through a national database of known DNA profiles.
The development comes as the search for Nancy Guthrie heads into its third week. The 84-year-old was last seen at her Arizona home on January 31 and was reported missing the following day.
Authorities say her blood was found on the front porch. Purported ransom notes were sent to news outlets, but two deadlines for paying have passed.
The glove discovery was revealed days after investigators had released surveillance videos of the masked person outside Guthrie's front door.
A porch camera recorded video of a person with a backpack who was wearing a ski mask, long pants, a jacket and gloves.
The FBI has described the man as about 5 feet, 9 inches (175cm) tall with a medium build. The agency said he was carrying a 25-litre Ozark Trail Hiker Pack backpack.
On Friday night local time, law enforcement agents sealed off a road about 3.2km from Guthrie's home as part of their investigation. A series of sheriff's and FBI vehicles, including forensics vehicles, passed through the roadblock.
The investigators also tagged and towed a Range Rover SUV from a nearby restaurant car park late on Friday. The sheriff's department later said the activity was part of the Guthrie investigation but no arrests were made.
Savannah Guthrie, co-host of NBC News' popular Today show, has posted several video messages with her brother Camron Guthrie and sister Annie Guthrie pleading for their mother's return and appealing for the public's help in solving the case.
In one video, they expressed a willingness to meet ransom demands.
The kidnapping has drawn intense media attention as well as expressions of sympathy and support from US President Donald Trump.
On Tuesday, sheriff deputies detained a person for questioning during a traffic stop south of Tucson, but he was later released. The same day, deputies and FBI agents conducted a court-authorised search in Rio Rico, about an hour's drive south of the city.
Authorities have expressed concern about Nancy Guthrie's health because she needs vital daily medicine. She is said to have a pacemaker and have dealt with high blood pressure and heart issues, according to sheriff's dispatcher audio on broadcastify.com.
Earlier in the investigation, authorities had said they had collected DNA from Nancy Guthrie's property which doesn't belong to Guthrie or those in close contact with her. Investigators were working to identify who it belongs to.
The FBI also has said approximately 16 gloves were found in various spots near the house, most of which were searchers' gloves that had been discarded.
With Reuters
