The Federal Trade Commission (FTC) recently issued a warning on a popular new cryptocurrency scam that tricks victims into sending money.

The FTC warning comes after high-profile celebrities’ and national leaders’ Twitter accounts were hacked earlier this month with scammers sending out fake tweets telling followers to send money using the cryptocurrency Bitcoin. Victims ranged from musician Kanye West to politicians Joe Biden and former president Barack Obama to Tesla CEO Elon Musk with hackers using their accounts to tweet out that followers would receive double the money back they transferred using Bitcoin. The followers were directed to send the Bitcoin to fraudulent accounts.

The FTC warns that once money is sent via Bitcoin or another type of cryptocurrency, the money is gone and there is usually now way to retrieve the money.

FTC officials said a tweet – or social media message, text, email or other communication – that requests you pay with Bitcoin is probably a scam. Other signs that the communication is a scam is that it guarantees you will make money, guarantees you will double your money or states you will get free money.

Officials are asking anyone who spots a cryptocurrency scam to contact the FTC immediately.