Amid the ongoing humanitarian tragedies of a decadelong Syrian civil war, a booming trade has emerged for "fixers" offering to help families locate or save their loved ones in Syria, where tens of thousands of people have disappeared into a murky web of Bashar Assad regime jails infamous for torture.

Police officers, lawyers, businesspeople and even lawmakers, with security and judicial contacts, demand steep fees to dig up information about a disappeared son or brother, allow a visit, reduce their sentence or obtain their release.

Some efforts are successful, while more often than not scammers pocket the money and stop answering phone calls.

It is normally families who seek out the so-called fixers, but sometimes they receive cold calls persuading them to pay up for a photo or voice recording, only to have the mysterious caller vanish with the money.

Syrian mother Umm Saeed was so desperate to find her two jailed sons she even sold the family furniture to pay fixers, but a decade of deceit has left her no closer to the truth.

"Had they asked for my heart, I would have handed it over," the 63-year-old mother told Agence France-Presse (AFP) by phone from central Syria, using a pseudonym for fear of reprisal. "They lied to me."

Saeed said her two sons were detained in 2012.

"Whenever someone told me about a potential middleman, I would go to them," said the mother, who suffers from heart problems.

She paid a lawyer who asked for the equivalent of more than $3,000 but "did not provide the slightest bit of information."

Another man claiming to be a police officer was paid with a mobile phone after saying he could get her permission to visit Sednaya, a notorious prison in Damascus.

But when she showed up at the jail, which Amnesty International calls a "slaughterhouse," she was told the pass was fake and sent away.

"I sold my home furniture and my daughters' gold. I have nothing left," she said.

Diana Semaan, a researcher at Amnesty, said the regime's policy of silence on the fate of detainees had created a "black market" for information.

"Families, desperate for information, end up paying huge amounts of money, sometimes their entire life savings, to intermediaries and 'middlemen' close to the Syrian government," she explained.

Suaad, 45, said her family in northern Syria had paid 20 million pounds ($15,900) to various brokers over the years to try to find her brother since he disappeared in 2013.

In April, someone contacted the family asking for payment to release him.

But after they raised the cash, "he told us my brother had died three days earlier," Suaad said.

Two weeks later, another person rang, offering a phone call with her brother.

When the call came, there was no audible voice on the other end of the line; all they got for their money was static.

The Syrian Observatory for Human Rights says around half a million people have entered regime jails since the 2011 start of Syria's conflict, of whom 60,000 have died of poor detention conditions or torture.

Another mother, 56-year-old Umm Yahya, said she had managed to visit her son just once, six months after he was detained in Idlib, northwest Syria, in 2012.

"I barely recognized him. His weight had dropped from 110 (240 pounds) to less than 50 kilos," she said.

She has heard nothing since.

Her family has over the years poured a small fortune into the pockets of possible intermediaries, selling two plots of land and a house in Idlib to cover the costs, but to no avail.

Her husband has grown increasingly reluctant to squander the family's savings. Two years ago, a lawyer asked for $10,000, but her husband refused.

"If a hundred more people turned up, even if there was just a one percent chance of success, I would do it again," said Umm Yahya.

Estimated $900 million in bribes

The Association of Detainees and Missing Persons at Sednaya prison accused the regime in a report earlier this year of using detention as a means to extort money and "increase the influence of security services, their leaders, influential people in its government, some judges and lawyers."

It carried out hundreds of interviews showing that families had paid a total of more than $2.7 million over the years in return for the promise of information, a visit or a release from jail.

Based on that figure, the association estimates that the Syrian regime has made almost $900 million through "extortion" of families over the past decade.

Noura Ghazi, director of Nophotozone, an association that helps detainees' relatives, said many lawyers "invested" in state security courts.

Most of them deceive the families, "but some pay bribes to judges and to the security apparatuses, while taking a percentage or just their fees, and succeed in getting a person released," she said.

Though most efforts fail, three people told AFP they had managed to transfer their relative to a better jail or even to have them freed.