Thousands of people are believed to have lost their savings after investing in a cryptocurrency trading app called iEarn Bot.
Experts who have investigated the company say it could be one of the largest crypto scandals to date.
Trading in cryptocurrencies has become popular, with people often promised large rewards over short periods.
But law enforcement agencies warn of a growing number of scams and recommend investors conduct "due diligence".
The money just disappeared'
Roxana, not her real name, is from Romania. She says she lost hundreds of euros when she invested in iEarn Bot. She asked not to have her identity revealed as she fears her professional reputation might be damaged.Customers buying the bots - like Roxana - were told their investment would be handled by the company's artificial intelligence programme, guaranteeing high returns.
"I invested in a bot for one month," Roxana tells the BBC. "You could see in the app how many dollars the app was creating: there were graphics showing how the investment was progressing.
"It looked quite professional until, at some point, they announced maintenance." At that point, for some time, withdrawals from the app were frozen.
"Some people started to say 'I cannot withdraw... what is happening'," explains Roxana. "I made the request to withdraw and the money just disappeared. The portfolio became zero - but I was never credited on my wallet with any money."
In Romania, dozens of high-profile figures, including government officials and academics, were persuaded to invest via the app because it was sponsored by Gabriel Garais, a leading IT expert in the country.
Mr Garais says he too was fooled into investing his own savings in the app and lost his money.
But Roxana insists, had it not been for Garais's sponsorship, she would have never considered investing.
"We had the knowledge to think this might be a scam," she says, "but the fact that, in between us and the company there was a reputable teacher, meant that we didn't check too much - we didn't doubt too much."
What happened in Romania is not an isolated incident. Nor is it unique to Romania.
When Silvia Tabusca, a Romanian organised crime expert from the European Center for Legal Education and Research, began looking into iEarn Bot, she discovered that many people in other countries had also lost their money in the scheme.
What surprised her most was the scale of the operation.
says Andres. "As the local leaders did not have answers, people started to get angry."
With the help of an analyst, the BBC managed to identify one main crypto wallet that received payments from about 13,000 potential victims, for a profit of almost $1.3m (£1m) in less than one year.
But we could not track down where and to whom the money went.
For investigators, this is a common issue.
"One of the challenges is to identify and attribute who the illicit actor is, where the value is going, and then being able to take investigative steps and law enforcement action," says John Wyman, chief of the FBI's new Virtual Assets Unit.
Investigations in this sort of scheme, he says, go global quickly.
Such investigations require international co-operation and may take longer, but he insists that those responsible are eventually up to justice.
The FBI set up the Virtual Assets Unit last year in order to respond to the growing number of crimes using virtual currencies.
It invites people who have been victims of scams to make a complaint on the FBI's dedicated page.
But law enforcement agencies maintain the best way to fight scammers remains prevention.
"Knowledge - and doing some due diligence before the investment - it's critical," says Mr Wyman.
"It's like everything else: if it sounds too good to be true, it often is."