TUCSON, Ariz. (AP) mdash; Law enforcement agents have been gathering more potential evidence as the search for ldquo;Todayrdquo; show hostnbsp;Savannah Guthrienbsp;lsquo;s mother heads into its third week.Nancy Guthrie, 84, was last seen at her Arizona home on Jan. 31 and was reported missing the f ollowing day. Authorities say her blood was found on the front porch. Purportednbsp;ransom notesnbsp;were sent to news outlets, but two deadlines for paying have passed.Authorities have expressed concern about Nancy Guthriersquo;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 sheriffrsquo;s dispatcher audio on broadcastify.com.Herersquo;s what to know about her disappearance and the intense search to find her:Most recent informationFriday night, the FBI and Pima County Sheriffrsquo;s Department briefly detained a man and searched a house a short drive from Nancy Guthriersquo;s Catalina Foothills neighborhood late Friday into early Saturday, but there was no arrest and no sign of Guthrie, law enforcement sources told ABC News.nbsp;The sources described the activity as ldquo;tracking leadsrdquo; associated with the Guthrie investigation. Additionally, a reward of up to $100,000 is available for information leading to the location of Nancy Guthrie as well as the arrest and conviction of anyone involved in her disappearance.Call tips in to 1-800-CALL-FBI or 520-351-4900.nbsp; nbsp;Video of masked manThe Federal Bureau of Investigationnbsp;released surveillance videosnbsp;of a masked person wearing a handgun holster outside Guthriersquo;s front door in Tucson the night she vanished. A porch cameranbsp;recorded videonbsp;of a person with a backpack who was wearing a ski mask, long pants, jacket and gloves.On Thursday, the FBI called the person a suspect. It described him as a man about 5 feet, 9 inches tall with a medium build. The agency said he was carrying a 25-liter ldquo;Ozark Trail Hiker Packrdquo; backpack.Investigators initially said there was no surveillance video available since Guthrie didnrsquo;t have an active subscription to the doorbell camera company. But digital forensics experts kept working tonbsp;find images in back-end softwarenbsp;that might have been lost, corrupted or inaccessible.Studying DNAInvestigators collected DNA from Guthriersquo;s property which doesnrsquo;t belong to Guthrie or those in close contact with her, the Pima County Sheriffrsquo;s Department said. Investigators are working to identify who it belongs to.Evidence requiring forensic analysis is being sent to the same out-of-state lab that has been used since the beginning of the case, the department said.Investigators found several gloves, the nearest about 2 miles (3.2 kilometers) from Guthriersquo;s home, and submitted them for lab analysis, the sheriffrsquo;s department said. It did not specify what type of gloves.The sheriff stressed his department is working closely with the FBI.Sorting through tipsThe Pima County sheriff and the FBI announcednbsp;phone numbersnbsp;and anbsp;websitenbsp;to offer tips. Several hundred detectives and agents have been assigned to the case, the sheriffrsquo;s department said.The FBI said it has collected more than 13,000 tips since Feb. 1, the day Guthrie was reported missing. The sheriffrsquo;s department, meanwhile, said it has taken at least 18,000 calls.The sheriffrsquo;s department has not said whether any tips have advanced the investigation.Intensive searchesLate Friday night, law enforcementnbsp;sealed off a roadnbsp;about 2 miles (3.2 kilometers) from Guthriersquo;s home as part of their investigation. A parade of sheriffrsquo;s and FBI vehicles, including forensics vehicles, passed through the roadblock.The investigators also tagged and towed a Range Rover SUV from a nearby Culverrsquo;s restaurant parking lot late Friday.The sheriffrsquo;s department said Saturday the activity was part of the Guthrie investigation but no arrests were made.On Tuesday, sheriff deputies detained a person for questioning during a traffic stop south of Tucson. Authorities didnrsquo;t say what led them to stop the man butnbsp;confirmed he was released.The same day, deputies and FBI agents conducted a court-authorized search in Rio Rico, about an hourrsquo;s drive south of the city.Family pleasSavannah Guthrie, her sister and her brother have shared on social medianbsp;multiple video messagesnbsp;to their motherrsquo;s purported captor.The familyrsquo;s Instagram videos have shifted in tone from impassioned pleas to whoever may have their mom, saying theynbsp;want to talknbsp;and are even willing tonbsp;pay a ransom, to bleaker and more desperate requests for the publicrsquo;s help.The latest video on Thursday was simply a home video of their mother and a promise to ldquo;never give up on her.rdquo;A quiet neighborhoodNancy 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 ldquo;Todayrdquo; in 2011.In a video, she described her mother as a ldquo;loving woman of goodness and light.rdquo;Permalink| Comments ...read more read less