Binance, the cryptocurrency exchange currently ranked second to OKEx on CoinMarketCap in trading volume, has temporarily suspended withdrawals and trading.

Changpeng Zhao, CEO of Binance, tweeted on Feb. 7 at 6:38pm EST that the exchange was experiencing a server error that could be resolved in a few hours and that “no data is lost.”

We experienced a server issue on our replica database cluster, causing some data to be out of sync. Need to fully resync from master. Due the size of the data, it will take several hours. No data is lost. We appreciate your understanding and support. — CZ (@cz_binance) February 8, 2018

About two hours later, Zhao tweeted that the new estimate for resolving the out of sync data was 10 hours. A separate tweet shortly after apologized to Binance customers for the system’s extended and unexpected downtime:

sorry guys, not something we want either. We didn't have a choice, other than trying to fix it as soon as possible for our users. One of our team literally threw up after the calculation arrived at 10 hours. https://t.co/P2YjkYDf9K — CZ (@cz_binance) February 8, 2018

Cryptocurrency exchange Kraken had experienced similar unexpected downtime in January, when a scheduled two-hour long system upgrade turned into a more than two day delay until the exchange went back online.

According to Binance’s official Twitter, trading activity is estimated to resume on Feb. 9 at 4am (UTC) (11:00pm EST). Customers will have 30 minutes before trading starts to withdraw orders.

Zhao has denied that any hack on Binance has taken place:

All because this didn’t do what it was suppose to do. Not hack. pic.twitter.com/gHW9fxaAQN — CZ (@cz_binance) February 8, 2018

Binance had seen a such large influx of new customers, adding 250,000 thousand in one day on Jan. 4 and 240,000 users in one hour on Jan. 13, that they temporarily suspended new user sign ups in early January. Exchanges Bittrex and Bitfinex have also stopped new users sign ups for the same reason.

Binance had been the world’s largest crypto exchange in mid-January, at one point hosting trading of almost $5 bln over a 24-hour period. OKEx now holds the number one spot for trading volume on CoinMarketCap, about $3.5 bln over a 24-hour period by press time, with Binance’s trading volume at about $2.1 bln over a 24-hour period by press time.