When Californian woman Sherri Papini was released by captors after three weeks, her husband said she had screamed for help "so hard that she coughed up blood".

In one of his first interviews since her release, Keith Papini told ABC’s 20/20 show that his wife had been chained up by her abductors, and when she had been released, she was thrown from a vehicle, tied up in chains with a bag over her head. She used that same bag to flag down a passing vehicle and get help. She was on the side of Interstate 5 in Yolo County, and it was Thanksgiving morning.

"She screamed so much, she’s coughing up blood from the screaming trying to get somebody to stop," said Mr Papini.

"And again just another sign of how my wife is, she’s so wonderful. She’s saying, 'Well maybe people aren’t stopping because I have a chain that looks like I broke out of prison,' so she tried to tuck in her chain under her clothes."

What local authorities have described as an "absolute miracle" - her return on Thanksgiving - also remains a mystery.

Shasta County sheriff Tom Bosenko said authorities were looking for a dark-coloured SUV and two Spanish-speaking women. They have a limited physical description of the suspects - one with pierced ears, one with straight black hair - and a sketch artist is to render their appearances.

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Authorities do not yet know where Ms Papini had been held during those three weeks, or if she had been moved. A motive has not been given.

The 34-year-old was bruised when she was taken to hospital, with a broken nose from multiple beatings, and she had lost a lot of weight. Her long blonde hair had been cut short. Most disturbing, perhaps, was that a "message" had been burnt into her skin. The injuries were confirmed by Mr Bosenko.

"She was chained anytime she was in the vehicle," Mr Papini said in the interview, which airs on 2 December.

"They opened the door, she doesn’t know [where] because she’s got a bag over her head. They cut something to free her restraint that was holding her in the vehicle, and then kind of pushed her out of the vehicle."

Her husband rang the alarm in November after his wife went for a jog in the local park and then did not pick up their two young children from daycare.

He appealed to Good Morning America, begging for her return and offering thousands of dollars for any information.

After the family was reunited in hospital, he told the same show: "Nothing could have prepared me for what I was about to see upon my arrival at the hospital, nor the details of the true hell I was about to hear."

He has since addressed what he described as "conspiracy theories", including accusations of his involvement and claims that the abduction was a hoax.

“I do not see a purpose in addressing each preposterous lie,” he said.

Speaking to KOBI-TV, the driver who discovered Ms Papini before sunrise on 24 November described how she found her: in a quarter inch-thick chain, her wrists in hose clamps.

"I see this blonde woman waving what looks like a brown flannel shirt up and down desperately trying to flag someone down," Alison Sutton said.