Former Wells Fargo Chairman and CEO Dick Kovacevich told CNBC on Tuesday that he believes bitcoin is a scam.

“I think it’s a pyramid scheme. It makes no sense. I’m just surprised it isn’t even lower,” he said on “Squawk on the Street.”

Bitcoin tumbled to a six-week low early Tuesday, falling below $12,000 for the first time since Dec. 5, according to CoinDesk, before paring some of those losses.

Comments from South Korea’s finance minister renewed concerns about a crackdown in one of the largest markets for digital currency trading.

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