The overall market capitalisation of all cryptocurrencies dropped substantially during the opening of European trading hours, falling 3% to a low of $1.049 trillion, as reported by Cryptoslate.
Bitcoin lost $22,000 as a result of its 6% negative decline.
The swing hit a three-week low of $21,400 at that point, which was for the market leader. Following a modest rally, the price of BTC momentarily increased to $22,000, Cryptoslate noted.
Relative Strength Index (RSI) fell to a record low of 38.53, not seen since July 12. As of this writing, there is increasing sell pressure, and a retest of the $21,400 support level appears impending.
Since nothing fundamentally new has happened at this time, it is difficult to determine what caused the decline.
(With insights from Cryptoslate)