(NewsNation) — The FBI has increased its reward to up to $100,000 for information leading to the location of Nancy Guthrie or the arrest and conviction of anyone involved in her disappearance, according to a new update from the Phoenix Field Office.

After a forensic review of doorbell camera footage, investigators say the suspect appears to be a man between 5-foot-9 and 5-foot-10 with an average build, wearing a black 25‑liter Ozark Trail Hiker Pack backpack.

The FBI says it has received more than 13,000 public tips since Feb. 1 and is operating a 24‑hour command post where examiners and agents screen each lead for credibility and actionable information.

New TMZ email contains ‘ominous’ remarks related to Nancy Guthrie case

Media outlet TMZ has reported getting another email, this time with “ominous” statements, from someone who says they know the identity of Nancy Guthrie’s kidnappers.

An earlier email sent to the outlet Wednesday demanded one bitcoin in exchange for information on Guthrie’s suspected kidnappers. A single bitcoin is worth roughly $65,000.

There do not appear to have been any deposits sent to the bitcoin account in the email.

The latest email contained what TMZ described as “ominous” remarks, with the sender complaining they were not being taken seriously. In the initial note, they stated they had tried to contact Guthrie’s children but had failed.

The website did not describe the remarks in detail but said it is working with law enforcement.

Nancy Guthrie case: New video shows man with backpacks

Also Thursday, NewsNation obtained surveillance video that seems to show someone carrying and wearing backpacks similar to those seen in the surveillance videos from Guthrie’s home, attempting to climb over a wall in Tucson at 1:52 a.m., which was minutes after Guthrie’s Nest camera disconnected at 1:47 a.m. and about 20 minutes before the system later detected a person at 2:12 a.m.

The Ring camera video recorded about five miles from Nancy Guthrie’s home is now on the FBI’s radar, with investigators examining its timing in relation to Guthrie’s disappearance.

The Pima County Sheriff’s Office said the video, like all video it has received, is being investigated.

Law enforcement officials have cleared the man seen in the video, according to two officials briefed on the matter, NBC News reported.

Sheriff in Guthrie case is withholding key evidence from FBI

An FBI official tells NewsNation that Pima County Sheriff Chris Nanos is blocking federal agents from accessing key evidence in the disappearance of Nancy Guthrie, hindering the bureau’s ability to assist in the case.

According to the official, the evidence — described by a source as including a glove, DNA and potentially more — has already been sent to a private lab in Florida for testing, and the FBI will have to retest it once it is returned, delaying the investigation.

“This is dumb,” the source told NewsNation, adding that the bureau stepped in at the sheriff’s request. “The FBI wants to find Nancy.”

The FBI asked Nanos for the evidence to be processed at the FBI’s national crime laboratory in Quantico, Virginia.

Outsourcing forensic analysis to a Florida contractor, effectively denying the access of the Federal Bureau of Investigation to crucial evidence in the case, is delaying the FBI ability to assist in the case, according to the official, Reuters reported.

Sheriff’s office asks for more video from neighbors

The Pima County Sheriff’s Office also sent an alert to those living in a two-mile area around Guthrie’s home, asking for video footage — including that of vehicles, vehicle traffic, people, pedestrians or anything else out of the ordinary — between Jan. 1 and Feb 2.

Earlier ransom deadlines already passed

Both messages to TMZ were sent after two ransom note deadlines passed. Investigators have not publicly confirmed whether the family had communication with the alleged kidnappers.

A ransom note, sent to TMZ and Tucson stations KOLD News 13 and another outlet earlier this week, demanded millions of dollars in bitcoin for Guthrie’s safe return. The note included a bitcoin wallet address where payment could be deposited.

They also have not verified whether the notes came from the person who abducted Guthrie.

FBI brings in forensic height camera

Earlier on Thursday morning, a forensic tent was set up outside Guthrie’s home, and an osteometric board was brought in as investigators continued efforts to find her.

Forensic tents are typically erected to protect and preserve evidence or to conceal a body, weapon or other critical evidence. An osteometric board, or forensic height board, is typically used to measure the length of long bones. These measurements are critical for estimating a person’s stature and for other forensic and anthropological analyses.

The Pima County Sheriff’s Office said it has received 18,000 calls regarding the case, with about 4,000 of those coming in the 24 hours following the release of surveillance photos and videos of a subject in the case.

Evidence in the Nancy Guthrie case

Released by the FBI, the photos and video show a masked individual appearing to tamper with the camera at Guthrie’s front door.

Guthrie did not have a subscription for her Nest camera, so the footage was not initially available to investigators, but the FBI stated it was recovered from backup servers.

On Wednesday, a black glove was located on a roadway about a mile and a half from Guthrie’s home. Authorities have not confirmed whether they believe it is connected to the case.

Nancy Guthrie reported missing on Feb. 1

Guthrie’s family, including daughter and TV anchor Savannah Guthrie, has released a video pleading for the public’s help in identifying the kidnappers.

Investigators believe Nancy Guthrie was kidnapped overnight before being reported missing on Feb. 1. A timeline from the sheriff’s office shows that she was dropped off at home by an Uber driver shortly before 10 p.m. on Jan. 31.

At 1:47 a.m. on Feb. 1, Guthrie’s doorbell camera disconnected. At 2:12 a.m., software detected a person on camera. At 2:28 a.m., Guthrie’s pacemaker disconnected from her phone.

The FBI is offering a reward of up to $100,000 for information leading to Guthrie’s recovery or the arrest and conviction of anyone involved in her disappearance.

Anyone with “actionable information” is asked to contact 1-800-CALL-FBI or the Pima County Sheriff’s Department nonemergency line at 520-351-4900.