They wanted to be models. Mostly struggling US college students, the young women submitted applications through websites such as BeginModeling.com - which promised a "comfortable start" in the industry - only to learn that the modelling job was a pornography shoot.

They agreed to participate anyway, federal authorities claim in court documents, because of a promise that the videos were being created exclusively for private collectors or DVDs sold abroad and would never be posted online.

That turned out to be a lie, the FBI says. The footage was uploaded within months to a website called GirlsDoPorn, which has allegedly made US$17 million (NZ£27m) by specialising in "amateur porn" starring nervous first-timers.

They also appeared on Porn Hub, one of the world's leading adult video sites. The women say they were horrified to find out their shoots were online; many were harassed or ostracised as a result. At least one was disowned by her family, according to the FBI.

The owners and two employees of GirlsDoPorn now face sex-trafficking charges in what federal investigators call a "scheme to deceive and coerce young women to appear in sex videos."

A criminal complaint filed last week in San Diego, US, where the company is based, alleges that some of the women were threatened with "legal action or outing" if they didn't perform, barred from leaving shoots or even sexually assaulted. They were often paid far less than the US$5000 (NZ$8000) or so that was initially offered.

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"The FBI is still in the process of identifying all the women recruited, filmed, coerced and defrauded by this conspiracy," the complaint says, "as well as the proceeds made from these activities."

Website owner Matthew Isaac Wolfe, 37, porn actor Ruben Andre Garcia, 31, and employee Valorie Moser, 37, were arrested last week.

The FBI says 37-year-old Michael James Pratt, the site's other owner, is a fugitive. He's believed to have fled the United States for New Zealand, where he and Wolfe grew up and were childhood friends. All could be sentenced to life in prison if convicted.

Attorneys for Garcia and Pratt either declined to comment or did not respond to inquiries from The Washington Post. Anthony Colombo Jr., who represents Moser, said in an email that his client "looks forward to addressing the charge in the future."

The allegations stunned others involved in the pornography industry, who described the company as an outlier. Alec Helmy, the president and publisher of XBiz, an adult-entertainment industry news site, called the case "a very strange story."

"Consent is a huge thing within the business for obvious reasons," he said. "And there are a set of standard practices that everyone kind of abides by, and so it's rather shocking to think that a seemingly full-fledged business was operating that way."

The criminal charges come as a civil trial against GirlsDoPorn and its owners is underway in San Diego Superior Court. The allegations in that case echo the criminal complaint: Women say that after responding to modelling ads, they were ultimately tricked into performing in pornography that was posted online.

In court, a woman identified only as Jane Doe 15 testified that her video spread quickly among her friends, family and classmates, according to the Daily Beast, which has reported extensively on the case. She was kicked off her cheerleading team and left her college town. She struggled in her relationships with family and friends.

"If I had known that not only was it going on the Internet," she said, "but that they were posting it on the Internet, that my name would be attached to it, that it would be in the United States, and that I wouldn't be paid US$5000, but US$2000 less, and insulted because I was pale and bruised; if I had known that it was more than 30 minutes of filming, if I had known any of that, just any one of those; if I had known that other girls had been harassed and kicked out of school for it, if I had known that I would be kicked off the cheer team; if I had known any of that, I wouldn't have done it."

There are 22 plaintiffs in the civil case. John O'Brien, one of the attorneys representing the women, told The Washington Post that their lives have been "totally turned upside down." He added: "Many of these women have gotten psychiatric help and counsellors. Quite a few of them have attempted suicide. . . . A lot of these girls have said their lives are ruined."

Pratt and others involved with GirlsDoPorn deny wrongdoing. They argue the women knew what they were getting into and signed contracts allowing the videos' online distribution, with Pratt attorney Aaron Sadock saying in opening statements that the women "knew the risks."

"The plaintiffs in their testimony show that they are aware of the inherent risks," he said, according to the Daily Beast. "They were aware of Paris Hilton, Kardashians, release of sex tapes. In other words, the plaintiffs' social-media presence, activities online, posting videos themselves make it clear that they inherently knew the risks of being filmed in an adult video."

But the FBI complaint claims the women were not given a chance to read the contracts or allowed to keep a copy, instead rushed into painful sexual encounters with an "aggressive and indifferent" Garcia. Some allegedly signed after company employees gave them alcohol or marijuana.

The company also paid Moser and other women to falsely claim that they themselves had filmed videos that no one ever found out about, the FBI alleges. In one alleged example, a woman going by the name of "Kailyn" wrote to a hesitant woman, "You're totally fine! That's what I was worried about but there is absolutely no way anyone will find out!"

O'Brien said that GirlsDoPorn, which he described as the "black sheep of the porn industry," built a business model and a customer base that relied on duping inexperienced young women into shooting sex scenes. The website often emphasises the youth or inexperience of the women, sometimes noting that they "took months of convincing."

"They don't want porn stars," O'Brien said. "Let's just say their target is the girl next door, the one and only time she's ever going to do porn. And the only way to convince somebody of that - to get a college girl that has no interest in porn, has never done porn to do that - is to set up the scheme they have."