Bitcoin has traded below $10,000 for the first time since early December.
The value of one bitcoin fell to $9,958 (£7,222) before making a slight recovery, according to the price index run by the news site Coindesk.
That represents a drop of nearly 50% since it peaked close to $19,800 five weeks ago.
Other crypto-currencies including Ethereum, Ripple, Litecoin and Bitcoin Cash have also experienced steep falls over the past day.
There has been concern among some experts that a bubble had been forming in the market as casual investors piled into an asset they did not fully understand.
More to follow