Bitcoin fell 3 percent Thursday afternoon along with other cryptocurrencies.
As of 3:14 p.m. ET, bitcoin was at $6,467.01, according to CoinBase. Last week, the largest cryptocurrency fell as low as $5,799.62, its lowest since mid-November.
There hasn't been any one catalyst to trigger a sudden sell-off in bitcoin, though digital currency-trading security breaches and regulatory scrutiny have weighed on cryptocurrencies after bitcoin's price ran up more than 1,000 percent last year.
Bitcoin offshoot bitcoin cash was down 6.9 percent, to $719.89, ethereum was down 2.78 percent, to $460.37, and litecoin was down 5.3 percent, to $82.16, according to CoinBase.