The number of bitcoin ATMs installed worldwide sank to a two-year low this month, according to data from AltIndex.

Since the end of last year, the number installed has dropped 7,000, or 17%, to 32,500, AltIndex said on Wednesday. That follows an increase from 34,500 at end-2021.

The U.S., which hosts the largest number of machines, saw the biggest drop. There are now about 26,700 machines in the country. Still, the world's largest economy still has almost 18 times the number installed across the whole of Europe, which hosts some 1,500.

AltIndex attributes the decline to controversies about their potentially criminal use. For example, scammers may advertise goods for sale on sites like eBay, ask buyers to deposit funds into a specific bitcoin wallet through ATM, and then vanish.

Brandon Mintz, the CEO and founder of publicly traded bitcoin ATM operator Bitcoin Depot (BTM) said the trend is due to some operators turning off unprofitable ATMs or going out of business altogether.

"This creates an opportunity for us that allows us to further increase market share through acquisitions and organic kiosk growth in additional retail locations,” he told CoinDesk in an emailed statement.

Read More: CEO of World's Largest Bitcoin ATM Operator Sees Industry Ripe for Consolidation