Nancy Guthrie live updates: Suspect's clothing may have been purchased at Walmart; family cleared

The FBI released new details about the suspect sought in the kidnapping of Nancy Guthrie, who was seen outside her front door early on Feb. 1, armed while wearing a backpack, mask and gloves.

"The suspect is described as a male, approximately 5'9" - 5'10" tall, with an average build," the FBI said Thursday. "In the video, he is wearing a black, 25-liter 'Ozark Trail Hiker Pack' backpack."

The FBI released several images of the type of backpack worn by the suspect alongside a still from Nancy Guthrie's doorbell camera video.

The FBI said it confirmed the new details "after a forensic analysis of the doorbell camera footage."

"We hope this updated description will help concentrate the public tips we are receiving," the FBI said.

The FBI announced Thursday it has increased the reward for information leading to Nancy Guthrie and/or the arrest and conviction of anyone involved in her disappearance to $100,000.

The reward was previously $50,000.

Since Feb. 1, the FBI said it has received more than 13,000 tips in the case.

The Pima County Sheriff's Department said "several items of evidence" have been recovered, including gloves. The evidence is being analyzed, authorities said.

The sheriff's department also said it is using the Neighbors app to reach out to residents who live within 2 miles of Nancy Guthrie. The department said it's requesting any video footage from Jan. 1 to Feb. 2 "that includes vehicles, vehicle traffic, people/pedestrians, and anything neighbors deem out of the ordinary or important to our investigation."

The FBI and the Pima County Sheriff's Department are looking into a video posted online that shows a man wearing a backpack about 5 miles from Nancy Guthrie's house shortly before her abduction, sources told ABC News.

The backpack on the video may be different from the backpack in the doorbell camera footage from Nancy Guthrie's house, sources said.

-ABC News' Aaron Katersky and Trevor Ault