What to know about the investigation into Nancy Guthrie's disappearance

TUCSON, Ariz. — A glove containing DNA found a couple of miles from the Arizona home of ''Today'' show host Savannah Guthrie 's missing mother appears to match those worn by a masked person outside her house the night she disappeared, the FBI said Sunday.

The development comes as law enforcement gathers more potential evidence in the search for Nancy Guthrie, 84, which heads into its third week.

Nancy Guthrie was last seen at her Tucson home on Jan. 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.

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.

Here's what to know about her disappearance and the search to find her:

Video of masked man and discovery of a glove

The FBI on Tuesday released surveillance videos of a person wearing a handgun holster outside Guthrie's front door the night she vanished. A porch camera recorded video of the person with a backpack who was wearing a ski mask, long pants, jacket and gloves.

On Sunday, the FBI said in a statement that a glove, found in a field near the side of a road about 2 miles (3.2 kilometers) from the home, had been sent off for DNA testing. The agency said that it received preliminary results Saturday and was awaiting official confirmation.

Late Friday, law enforcement agents sealed off a road about two miles (3.2 kilometers) from Guthrie's home as part of their investigation. A series of sheriff's and FBI vehicles, including forensics vehicles, passed through the roadblock.

Investigators also tagged and towed a Range Rover SUV from a nearby restaurant parking lot. The Pima County Sheriff's Department said the activity was part of the Guthrie investigation.

Studying DNA

Investigators collected DNA from Guthrie's property which doesn't belong to Guthrie or those in close contact with her, the sheriff's department said. Investigators are working to identify who it belongs to.

The FBI has said approximately 16 gloves were found in various spots near the house, most of which were searchers' gloves that had been discarded.

Sorting through tips

The Pima County sheriff and the FBI announced phone numbers and a website to offer tips. Several hundred detectives and agents have been assigned to the case, the sheriff's department said.

The FBI said it has collected more than 13,000 tips since Feb. 1. The sheriff's department, meanwhile, said it has taken at least 18,000 calls.

The sheriff's department has not said whether any tips have advanced the investigation.

The same day, deputies and FBI agents conducted a court-authorized search in Rio Rico, about an hour's drive south of the city.

Family pleas

Savannah Guthrie, her sister and her brother have gone on social media and shared multiple video messages to their mother's purported captor.

The family's Instagram videos have shifted in tone from impassioned pleas to whoever may have their mom, saying they want to talk and are even willing to pay a ransom, to bleaker and more desperate requests for the public's help. A video on Thursday was simply a home video of their mother and a promise to ''never give up on her.''

And on Sunday night, Savannah Guthrie posted an Instagram video in which she issued an appeal to whoever abducted her mother or anyone who knows where she is being kept. ''It is never too late to do the right thing,'' Guthrie said. ''And we are here. And we believe in the essential goodness of every human being, that it's never too late.''

Nancy Guthrie lived alone in the upscale Catalina Foothills neighborhood, where houses are spaced far apart and set back from the street by long driveways, gates and dense desert vegetation.

Savannah Guthrie grew up in Tucson, graduated from the University of Arizona and once worked at a television station in the city, where her parents settled in the 1970s. She joined ''Today'' in 2011.

In a video, she described her mother as a ''loving woman of goodness and light.''