Update 28 July: As suspected, it seems that at least one of the listings for "trafficked girls" on this site is not real. A reader on Twitter (who has since deleted their tweet) and a commenter on this article have shared a link to a porn video that appears to feature the same blonde girl presented on the site as "Nicole." The suspiciously staged-looking photos appear to be screenshots of this video.

"Do not contact us just to ask questions," the site continued. I decided to pose as a potential customer to see what I could learn about these so-called dark web human traffickers.

After having landed on the site, users are met with a cornucopia of different services: weapons, drugs, bombings, assassinations, new identities, and trafficking. A feed of news updates apparently stretching back years is also listed. "Black Death enters Deep Web," the site read on 27 January, 2010. "And we are here to stay." After this, the site apparently changed addresses several times. "We will do it any time we are getting too popular," it said.

I found Black Death after a link was posted on Reddit . "Apparently they're an organized crime group that deals in nearly anything, you name it," the post read.

"I'm interested in the girl," I told the site owners in an encrypted email, "want to see more photos first." It didn't take long for a reply to hit my inbox.

The advert for the upcoming auction included Nicole's breast size, weight, and that she is free from sexually transmitted diseases. She was being showcased on the dark web, on a site run by a group calling itself "Black Death."

"Nicole's starting bid is set at 150,000$," the listing read. The girl, skinny, blonde, and topless, appeared to be thrashing around in the accompanying photos. With her arms tied behind her back, and the rope connected to a wire frame, "Nicole" lurched forward as the shadow of a man loomed in the background.

"The dark web, as it's known, is not somewhere that we pick up a lot of stuff from," a tactical advisor from the National Crime Agency's UK Human Trafficking Centre (UKHTC) told me over the phone. The NCA requested that we did not name the advisor as advisors' names are not publicly known.

After keeping the conversation going through emails, I was eventually given a list of detailed instructions for the auction. I was required to pay an upfront deposit to view a livestream of the girls. I asked to be let in at no cost, but this was denied.

"Do not bother us again," they wrote. And then, the site disappeared. "Black Death has moved," a placeholder on the site read.

After more exchanges over several days, and with me fabricating evidence that I possessed hundreds of thousands of dollars worth of Bitcoin, Black Death made it clear they wanted nothing to do with me.

In the short time after I initially contacted Black Death, another girl was added to the site, this time with a starting bid of $180,000. All of the images were high quality, complete with dramatic lighting. They also contained no identifying pieces of metadata, and a reverse image search did not return any results.

"Who are you, how do you know about us? Who recommended us?" the owners barked in their email response.

He said the UKHTC has seen similar sites, selling male and female slaves, sometimes with indications that the victims are being trafficked for sex work, on more open sites. Indeed, the trading of people online is not new. Social networks and online back pages have been used to facilitate human trafficking for years.

Apart from the dramatic photos, there wasn't a great difference between the Black Death site and auction sites already known to the UKHTC, the advisor said.

"I don't think for one minute if you send [the money] you're ever going to see it again."

But experts were not totally convinced that the site was legitimate. It was the glossy, high quality photos that immediately rang alarm bells for the UKHTC advisor, who felt that they were "probably staged." On other sites, the people being traded "will not be glamorized in the way these girls are," he added.

There are other problems with the Black Death site too. "The bizarre thing with this is they tell you where they were kidnapped and where they are based," the advisor noted. The site claimed that the American victims were abducted in Paris. "I would think there would be a lot of high profile media around the disappearance of American citizens in Europe," he said.