Prices for bitcoin tumbled Thursday, moving well below $4,000 on heavy volume.
Bitcoin fell 9% to $3,686 over the previous 24 hours, according to Coinmarketcap.com.
Prices for other so-called cryptocurrencies fell as well.
On Sunday, Bitcoin worked its way above $4,000 for the first time since before Christmas.
A year ago, bitcoin was trading close to $15,000.