Bitcoin, Ethereum and XRP fall sharply after Coinmarketcap.com removes data from some South Korean exchanges.

Prices for some of the most popular cryptocurrencies dropped sharply Monday. One apparent reason: an adjustment from a popular website on its digital-currency price quotes.

A website called coinmarketcap.com on Monday removed data from some South Korean exchanges from its price quotes for a range of virtual currencies including bitcoin, Ethereum and Ripple’s XRP. The move followed a South Korean government crackdown on cryptocurrencies.

The move by coinmarketcap caused some amount of chaos when prices across the board suddenly plunged. In mid-Monday trading, XRP had fallen 26% over the past 24 hours, Bitcoin Cash was down 18%, and litecoin was down 12%. Of the top 40 cryptocurrencies, 31 were down, including bitcoin and Ethereum.

A representative of the website confirmed the moves in an email to The Wall Street Journal, citing “extreme price discrepancy” among South Korean exchanges. The company added in a tweet Monday afternoon that it “excluded some Korean exchanges in price calculations due to the extreme divergence in prices from the rest of the world and limited arbitrage opportunity.”

Coinmarketcap has become one of the most popular destinations for price quotes as the sector surged last year. According to Amazon’s web-ranking service, coinmarketcap is currently the 154th most popular website in the world, in the same ballpark as Chinese retail giant Alibaba.com .

The website’s rejiggered prices led to a flip in market-value rankings on the site. Ethereum, with a $109 billion total market valuation, moved into second place, the spot previously occupied by XRP, which fell to third place with a $97 billion market value. Bitcoin remained number one, with a $255 billion market value.

More than $100 billion of the sector’s total market value was erased over the last 24 hours, according to the site. On Sunday, it stood at $835 billion. On Monday, it fell to as low as $683 billion, and lately was at $722 billion.

Before Monday, for example, prices for XRP on coinmarketcap were quoted as high as $3.84 on Jan. 4. About 25% of XRP’s trading volume came from the Seoul-based online exchange Bithumb, according to coinmarketcap.

On Monday, without the Korean-exchange data, the XRP price fell to about $2.50, and at one point on coinmarketcap.com, fell below $2.10. On Ripple’s website, the company quoted XRP at $2.41, with its source being a weighted average of prices on the U.K. exchange Bitstamp.

In 2017, South Korea and Japan became major markets for bitcoin and other cryptocurrencies, at the same time that China was clamping down on the sector. The flood of new money and enthusiasm in these countries led to price quotes that were higher, sometimes by hundreds of dollars, than on exchanges elsewhere. In Korea, this gap was nicknamed the “kimchi premium.”

In Japan, authorities embraced the sector, implementing rules for proper trading of bitcoin and other cryptocurrencies. In South Korea, though, the government has been more concerned with the potential for criminal activity tied to cryptocurrencies, and even retail investor losses amid a global mania and what many fear is a bubble in the sector.