An unexpected call from law enforcement can trigger immediate worry. This summer, the San Antonio Police Department (SAPD) warns that some people are capitalizing on that fear to scam Texans out of thousands of dollars.

In the Lone Star State and beyond, authorities say there has been an increase in reports of individuals impersonating government agencies, utility providers, and courts, then pressuring residents to deposit money into an ATM. In particular, the fraudsters have been getting victims to put their cash into a Bitcoin ATM or to send cryptocurrency, threatening that it’s the only way to avoid arrest.

Once sent, Bitcoin and other cryptocurrency transactions are generally irreversible, making recovery of stolen funds extremely difficult,” SAPD said in a press release, adding that people should share the message with family members, friends and older adults because it’s happening so frequently.

On Wednesday, July 1, the San Antonio City Council unanimously approved an ordinance intended to help protect Texans from the threat. It requires all businesses operating or housing virtual currency kiosks in San Antonio to display fraud-prevention signage in clear view of users, or face fines ranging from $100 to $500 per violation.

It is especially dangerous because these scams are “fast, untraceable, and almost impossible to reverse,” San Antonio District 7 Councilmember Marina Alderete Gavito wrote in a statement. Many who have been affected feel they have no other choice but to comply with the caller. The perpetrator often issues statements that create panic and urgency, targeting seniors and vulnerable community members.

“These signs are a simple yet impactful step that will keep many from losing thousands,” Gavito said.

Bitcoin is not inherently a scam; it is a form of cryptocurrency, defined by the Federal Trade Commission (FTC) as “a type of digital currency that generally exists only electronically.” A person can purchase it using a phone, computer or a cryptocurrency ATM and store it in a digital wallet. People use it to make quick payments, avoid transaction fees charged by banks or conduct anonymous transactions, the FTC said on its website. Others hold onto it as an investment, hoping its value will rise over time.

However, it is an extremely common tool that fraudsters use to trick others into handing over funds. The FBI considers it “the most prevalent and damaging fraud schemes today,” according to its website.

Legitimate government agencies and businesses will never ask for immediate payments via Bitcoin ATMs or cryptocurrency transfers. SAPD says that if someone contacts them and demands payment through a Bitcoin ATM, they should stop communicating with that person immediately and contact 911.