UPDATE (22nd May, 17:2opm GMT): A representative from Bitfinex has indicated it has generated a new hot wallet on a “failsafe machine”. It expects deposits and withdrawals will be live “soon”, after the wallet has successfully synced.

Popular bitcoin exchange Bitfinex today urged customers to halt deposits while it investigates a suspected hack.

In a statement released this morning, the Hong Kong-based company said the keys to its hot wallet “might have been compromised”. However, the majority of customers’ funds would not be affected, it said.

“Although we keep over 99.5% of users’ BTC deposits in secure multisig wallets, the small remaining amount in coins in our hot wallet are theoretically vulnerable to attack […] Although this incident is unfortunate, its scale is small and will be fully absorbed by the company.”

This year saw both Coinapult and Bitstamp lose funds in hot wallet thefts, with an estimated total loss of $5.4m at the time of reporting.

Currently the third most popular global bitcoin exchange, Bitfinex’s 24-hour volume stands at 15,905.02 BTC ($3.7m), according to BitcoinCharts.

A 0.5% loss on these trades works out at roughly $18,500. However, data from CryptoWatch and BitcoinWisdom suggests some variation in the exchange’s global volume and its potential loss. Both list volume figures closer to 10,500 BTC.

Bitfinex said it was working to create a new hot wallet for the deposits it stores online.

The exchange, which recently partnered with AlphaPoint to overhaul its back-end, is expected to release further updates in the coming hours.

Additional reporting by Pete Rizzo.

Correction: A previous version of this article stated that Bitfinex was the third most popular exchange by volume.

CoinDesk is following this developing story.