Popular cryptocurrency exchanges OKEx has suspended all cryptocurrency withdrawals indefinitely, as one of the trading platform’s private key holders has “been out of touch” with the exchange because they are “cooperating with a public security bureau in investigations.”

Most top cryptocurrencies saw their price drop on the news, with bitcoin dropping over 3% in 230 minutes on OKEx before recovering shortly after. The private key holder’s being out of touch has reportedly prevented withdrawals from being complete from the exchange, according to a notice OKEx published.

The notice adds that other functions on the exchange remain stable and that the security of users’ cryptoassets wasn’t affected. Withdrawals are set to restart “once the concerned private key holder is able to authorize the transaction.”

On social media, OKEx CEO Jay Hao claimed the private key holder is cooperating with authorities over a “personal issue,” and that the investigation would not affect the exchange’s business. Hao added that non-cryptocurrency withdrawals and all other OKEx operations remain unaffected.

Speaking to CryptoGlobe OKEx assured users the funds are safe and that it will be providing updates on the matter and restoring withdrawals “as soon as possible.” The exchange added it continues to “uphold our commitment to delivering first-class products and services to our users and would like to thank you for your patience and support at this time.”

Hao added:

We understand that the suspension of withdrawals directly impacts our users’ experience on OKEx, and we wholeheartedly apologize for this. All other activities — including deposits, spot trading, derivatives, staking, etc. — remain unaffected, and we would like to provide our assurance to all our customers that their funds are safe.

On social media, speculation is abuzz after large transaction monitor Whale Alert detected a deposit of 21,000 ETH (nearly $8 million) to OKEx, and the withdrawal of 50 million TRX ($1.3 million) and 1,180 BTC ($13.5 million) before withdrawals were halted.