In the photo, a gun and sneakered foot press Mulugeta’s head to the floor. There’s blood running across his face, and what looks like vomit congealing below his mouth. His feet and wrists are chained together behind his back.

This was the image of the 27-year-old Eritrean that was uploaded to Facebook in October, when Mulugeta’s family realized they had exhausted all other options to raise ransom money. They’d already sold their house and jewellery, while begging in churches, mosques and markets. Eventually, Mulugeta told the smugglers he couldn’t pay anymore, so they took a photo of him to send to his family; they knew they could put it on Facebook to raise money from friends. “The smugglers want money, they don’t care how the money is got,” Mulugeta, who asked to only go by his first name for security reasons, tells TIME.

By the time he was released in November, after being repeatedly sold between smuggling groups in Libya, Mulugeta had paid $18,400 to five different smugglers—more than $4,000 of which was raised through crowdfunding on social media. He’s now in a detention center in southern Tripoli, and spoke to TIME through Facebook messages, saying he’s still worried for his future and can’t return to Eritrea, where he fled from indefinite military service in a regime condemned for gross human rights abuses.

Hundreds of thousands of African migrants and refugees have tried to escape war, dictatorships or poverty, by heading for Europe in recent years: and social media is raising the cost. Their journeys often involve long and dangerous drives through the desert, and months or years in a smuggler’s camp, before they’re allowed get in flimsy boats to try and cross the Mediterranean. Throughout this journey, technology is both a blessing and a curse: it could be a lifeline to ask for help with, or a means for their families to witness their abuse, suffering and anguish in real time. Facebook, in particular, can offer a glimmer of hope to refugees who are trapped and desperate, because of how easy it is to reach lots of people in a short space of time.

Smugglers in north Africa see refugees and migrants as a commodity. Tens or even hundreds of thousands of people are thought to have been held captive by smuggling gangs, who demand hefty ransoms, and torture those who can’t pay up. As in Mulugeta’s case, relatives and friends of those held captive are increasingly turning to Facebook to raise the sums.

In photos posted online, men or women, sometimes blindfolded, have their faces pressed to hard ground. Videos show men jolting as they’re tortured with hot plastic, before the camera zooms in on their face. In one picture, a couple sits with their children, the asking price for their lives written in the text over their head: $4,400.

Victims and experts say people in Libya, Sudan and northern Niger have all used Facebook to raise ransom money, and that Eritreans, Ethiopians, and Somalis are the most likely to be held captive like this.

TIME has seen eight posts since late November, each shared hundreds or thousands of times between the Eritrean diaspora, with instructions on how to donate directly to a captive’s family. Once the full ransom is collected, it is usually transferred to a bank account in Dubai, or to Khartoum or Istanbul through the hawala system, an alternative money exchange channel that exists outside normal banking and is difficult to trace. From there, it moves on to the smuggling gangs.

“Many traffickers look at Eritreans, Ethiopians and Somalis with a dollar sign on them,” says Mark Micallef, a senior researcher at the Global Initiative Against Transnational Organized Crime. Experts say this is because those countries have large, well-connected diasporas, who are more easily able to access and raise money.

It’s impossible to know how many people are being held for ransom at any particular time, Micallef adds, but said it’s possible that tens of thousands of Eritreans have been held hostage in past years. He also suggested the fundraising potential of Facebook, and sometimes WhatsApp, could be encouraging smugglers to increase their financial demands.

“This desperation, and the fact that another pool of money has been accessed in the long term, is also fueling this spiraling of ransom,” says Micallef, who has been researching human smuggling and trafficking in north Africa for several years.

“This is a really sad and complex issue and one that we’re aware of which holds various consequences on all sides,” a Facebook spokesperson said in response to screengrabs of the posts by TIME. “Without specific links to the content it is difficult to fully assess the situation. However, we remain fully committed to working to understand the challenges and how we address these.”

As smuggling routes close down in Libya, partly because of European Union spending aimed at decreasing arrivals to Italy, militias who once offered a service in moving people are increasingly turning to violence and torture to make a profit.

“After the long journey from the entrance of Libya, to the main camps in [northwest town] Bani Walid, [the smugglers] start counting people, giving deadlines to pay ransom,” says a teenage boy from Somalia, who was held by smugglers for five months, and is now in Tripoli trying to reach Italy. (Like others interviewed for this report, he asked to remain anonymous because he is worried about his safety) “When the deadline is approaching they start torturing people with a lot of ways. First they start to tie people and beat them with metal, then electrocute [them].”

One Sudanese man, currently in a detention center in Tripoli after he was intercepted trying to cross the Mediterranean Sea, says detainees’ families have raised as much as $35,000 in various instalments, and one Somali woman had paid $60,000 in total. Everyone in detention with him has paid at least $3,000, he says.

“There were people [held] with me, when their family couldn’t pay money they post on Facebook and they get help,” says a 28-year-old Eritrean, who also requested anonymity. He was held by smugglers for more than a year and is now in a detention center in Tripoli. “If you don’t pay fast [smugglers] force you to to post your picture on Facebook. They give you a deadline to pay the money or tell you that they will kill you.”

Eritreans are also held for ransom in Sudan, where a lack of security means some are abducted directly from refugee camps.

The last smuggler Mulugeta was held by was Abdallah, a Libyan who seems to be well known for abuse by many Eritreans in contact with TIME from Tripoli detention centres. Mulugeta says he witnessed 12 people die in captivity. “I saw many bad things.”

Other Eritreans say Abdallah impregnated 18 girls and women in one group through rapes. A former captive, who sent TIME photos of her injuries, said Abdallah electrocuted her on her breast after she tried to resist an assault by him.

In Khartoum, older Eritreans say their children are being “kidnapped” by smugglers, who offer go-now, pay-later travel arrangements, meaning young people may be encouraged to travel to Libya without having to pay money up front. Sometimes, the first confirmation parents get that their daughter or son has left is through photos of them chained and injured, along with a price tag for their release.

Meanwhile, Libyan smugglers continue to use Facebook profiles to advertise trips to Italy. One man, identified by refugees as a smuggler, posts pictures of boats and lifejackets, while saying a journey from Libya to Italy will take 7-8 hours and cost 3500 dinar ($2,520).

For Mulugeta, Facebook offered a lifeline when he most needed it. “I used it to save my life, to ask help from all friends, family, and kind people.” He says he won’t feel properly safe until he’s evacuated from Libya. But many of his friends are still being held by smugglers.

“It’s not only my history,” he says. There are countless others with stories like his. “Please all the world watch us. We need your help. We are in danger.”

Contact us at letters@time.com.