Disturbing details continue to be revealed about the bizarre kidnap and torture of Californian mother Sherri Papini, who was found alive on Thanksgiving morning after disappearing three weeks earlier.

Among her extensive injuries, the 34-year-old mother-of-two had a "message" branded onto her skin, Shasta County Sheriff Tom Bosenko said.

"I would think that was some sort of either an exertion of power and control and/or maybe some type of message that the brand contained," Mr Bosenko told America's ABC News on Wednesday morning.

Sherri and her husband Keith Papini. Photo / Facebook
Sherri and her husband Keith Papini. Photo / Facebook

"It is not a symbol, but it was a message."

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Mr Bosenko declined to elaborate on the brand's appearance.

A former FBI special agent, Brad Garrett, believes the markings were a way for her captors to destroy her identity.

"The branding is so she will become part of their group; they want to eliminate her past. They cut her hair, they simply starved her, they beat her, maybe torture, etc. And it's to make her part of whatever they are," he told US breakfast show Good Morning America.

Police investigating the alleged abduction were "blindsided" by a graphic statement released by her husband Keith Papini on Tuesday, in response to accusations the incident was staged.

Mr Papini described his wife's horrific injuries in minute detail, from the "bruises ranging from yellow to black because of repeated beatings" to the "severe burns, red rashes and chain markings" on her emaciated, 39kg body. He also said her "signature long blonde hair had been chopped off".

Addressing the revelations regarding Mrs Papini's physical appearance, Mr Bosenko described those responsible as "a very sick person".

"Obviously, a very sick person who may have wanted to not only to cut it off to change her physical appearance, but also as to humiliate them, wear her down," he said.

Mrs Papini was allegedly abducted while taking a routine jog along the Mountain Gate trail near her home in Redding, northern California, on November 2. She was found on the side of a highway on Thanksgiving Day morning - more than 240km from her home - after a passing motorist spotted her and called 911.

Sherri Papini with her husband Keith and their two young children. Photo / Facebook
Sherri Papini with her husband Keith and their two young children. Photo / Facebook

Mrs Papini told police she had been thrown from a dark coloured SUV by her captors, whom she described as two Hispanic women armed with a handgun.

As the search for her alleged kidnappers intensifies, experts say the case is baffling for a number of reasons.

"Releasing this victim after holding her for a pretty extended period of time does not make sense to me, it just doesn't," former FBI agent Mary Ellen O'Toole told ABC News. "Because it really does increase the risk level of the offender exponentially."

Former FBI special agent Brad Garrett said it was baffling that Mrs Papini's alleged abductors decided to release her after 22 days.

"We don't know the circumstances. Did these two women - are they part of this group, organisation, whatever it might be - decide this is too much? They pick her up and place her along the side of the road, so the context of these two women is unclear," he told Good Morning America.

Mr Garrett weighed in on the possibility that more than two people were involved in Mrs Papini's abduction, which he described as an "opportunity grab" and said appears to be a "random" attack.

"There's too many steps. To go through the starvation, the branding, the cutting of the hair. It's like, 'I'm trying to make you part of whatever we are'. Whatever the group, whatever their extremist thinking might be, and the longer you do that, the person then becomes more dependent on you to survive and that's what they want."

Addressing a range of conspiracy theories that have surfaced, including speculation that the abduction was staged by the couple for financial gain and national fame, Mr Garrett said he didn't believe it to be true.

"If you're going to disappear, why go to this much trouble? Are you going to have someone brutalise you, brand you, starve you? Not likely."

Sherri Papini who was found alive on Thanksgiving, three weeks after her apparent abduction. Photo / News Corp Australia
Sherri Papini who was found alive on Thanksgiving, three weeks after her apparent abduction. Photo / News Corp Australia

Mr Papini shocked police involved in the investigation when he went public with explicit details surrounding his wife's injuries in a written statement to Good Morning America on Tuesday.

"There's some unique information in there that was in his press release today that we were hoping to keep a tight rein on as far as what we were going to release to the public," Shasta County Sheriff's Office head of investigations Anthony Bertain said.

"It's not the first hurdle in this investigation that we've had. We've overcome many of them, not just in this case, but there's surprises in all investigations, so this just wasn't good timing."

According to the FBI, there were close to 85,000 missing persons cases in the US in 2015. Over 18,000 of those were involuntary abductions. Only half of those victims returned home alive.

Mr Bosenko said investigators interviewed Mrs Papini for a third time on Tuesday and are hoping to get more information on the description of the two suspects soon.