Two Estonians have been arrested and are facing extradition to the US after being accused of defrauding thousands of people out of around $575 million with a crypto Ponzi scheme, according to the US Department of Justice. Sergei Potapenko and Ivan Turõgin, along with four unnamed co-conspirators, were allegedly behind a scam crypto mining company called HashFlare and a fake crypto bank project called Polybius.

The scheme began in 2013 when Potapenko, Turõgin, and the others started a company called HashCoins, according to an indictment, which you can read in full below. HashCoins said it built cryptocurrency mining equipment, though the DOJ says it actually only “sometimes” resold equipment and components that it bought off the shelf. By 2015, though, the indictment says that HashCoins had customers who were unhappy that they hadn’t received the mining equipment they’d purchased.

Enter HashFlare. Potapenko, Turõgin, and the others allegedly told some customers that instead of getting a physical machine, they’d get a share of profits from a sort of mining-in-the-cloud pool the company was running. Other people could sign up and pay for HashFlare as well, and they did, according to the incitement — the alleged fraudsters are accused of collecting around $550 million from customers, in both regular fiat money and crypto.

Unlike some other schemes, the DOJ says HashFlare did actually mine some crypto, just not anywhere near the amount it said it was (the indictment says it mined Bitcoin at “less than one percent of the hashrate sold to customers” and Ethereum and other coins at less than 3 percent). HashFlare’s website allegedly showed customers a bunch of statistics about the mining pool’s performance and told them they could withdraw the funds they supposedly earned. According to the indictment, though, the company “resisted” when people tried to take their money out (including by citing know your customer regulations) or would purchase crypto coins using other customers’ money and send those instead.

In 2017, HashCoins announced that it was holding an initial coin offering, where it’d sell tokens to raise funds so it could start something called “Project Polybius,” a “fully digital bank” that used the blockchain. (It’s an interesting name — in pop culture, the word Polybius is mainly associated with a famous video game hoax; not exactly the type of thing you’d want associated with what you’re asking people to invest in.) The indictment accuses Potapenko, Turõgin, and co. of taking at least $25 million people invested in the project and transferring it to themselves.

The conspirators “used the laundered proceeds to fund an extravagant lifestyle,” according to the indictment. It later elaborates on that, saying that the funds were used to purchase some relatively high-end cars (such as an Audi A7 Sportback, several SUVs from Audi, BMW, and Lexus, and — of course — an AMG G Wagon), as well as dozens of properties in Estonia.

Potapenko and Turõgin are facing charges of conspiracy to commit wire fraud, conspiracy to commit money laundering, and 16 counts of wire fraud. As for the victims of the alleged scheme, the FBI is asking people who transacted with HashFlare to fill out a form with information on how much money they spent with the company. It’s currently not making any promises about them getting that money back, though the government has worked to get some money back for victims of other scams.