U.K.-based cryptocurrency exchange Exmo detailed on December 21, 2020, the firm had “detected suspicious withdrawal activity” and halted withdrawals. Exmo said a security audit report revealed “large withdrawals” of bitcoin and five other cryptocurrencies. Analysts estimate that Exmo may have lost over $10 million from the hot wallet breach.

On Monday, the U.K.-registered digital currency trading platform Exmo disclosed it suffered a loss “some amounts of BTC, XRP, ZEC, USDT, ETC, and ETH.” According to the exchange, team members monitoring the hot wallets “spotted some large withdrawals” at approximately 2:27:02 UTC.

“The affected hot wallets comprise near 5% of the total assets. Let us stress that all the assets in the cold wallets are safe,” Exmo wrote in the security incident report.

The exchange added:

Most importantly, we want to assure you that if any user fund is affected by this incident, it will be covered completely by Exmo.

Exmo also provided a list of cryptocurrency addresses in the blog post and according to The Block’s research analyst, Igor Igamberdiev, the exchange lost roughly $10.5 million in digital assets. Exmo is asking digital currency services and exchanges to block the listed crypto addresses that are connected with the compromise.

The trading platform accounts for $43 million (1,890 BTC) in 24-hour trade volume according to market aggregators. Founded in 2013, Exmo claims to have 1.6 million registered users and roughly 50,000 daily traders.

At the moment, Exmo says the team is investigating the incident and will keep the address list updated.

“We reported the case to the London police this morning and keep in touch with the cybercrime team there,” Exmo said. “We [will] also conduct a thorough security review that will include all parts of our systems and data,” the exchange added. Exmo was recently granted temporary registration status from the U.K. Financial Conduct Authority.