(CNN)– Hackers have carried out a heist on a leading digital currency platform, making off with an unspecified amount of bitcoin.

NiceHash, which describes itself as the largest marketplace for mining digital currencies, said late Wednesday that it was suspending its operations for at least 24 hours because of a security breach.

The site’s payment system was compromised and the contents of its bitcoin account have been stolen, it said.Cryptocurrencies are virtual “coins” that are “mined” by computers using complex algorithms. Bitcoin is the most popular one.

NiceHash provides a platform for users to mine for other cryptocurrencies and get paid in bitcoin. That could involve significant sums: it paid out millions of dollars in bitcoin every week, according to its official Facebook page.

The site said it was still working to figure out exactly how many bitcoins were taken. The digital currency’s value has soared in recent weeks, crossing $15,000 for the first time on Thursday morning.

CoinDesk, a site specializing in cryptocurrency news and data, reported that NiceHash users were circulating a link to a bitcoin account that suggested as many as 4,736 bitcoins had been stolen, an amount worth roughly $71 million at current prices.

It wasn’t immediately clear whether funds had been taken from NiceHash users’ accounts as well.

“While the full scope of what happened is not yet known, we recommend, as a precaution, that you change your online passwords,” NiceHash warned users.

“In addition to undertaking our own investigation, the incident has been reported to the relevant authorities and law enforcement and we are cooperating with them as a matter of urgency,” it said.

NiceHash didn’t immediately respond to a request for further comment about the hack. The cyber heist is yet another reminder about the vulnerability of some digital currency platforms.

Bitfinex, a Hong Kong-based bitcoin exchange, was briefly shut down last year after hackers stole nearly 120,000 bitcoins — worth more than $65 million at the time.

The year before, cyber thieves made off with about 19,000 bitcoins after breaking into European exchange Bitstamp.

Cybersecurity firm FireEye warned recently that North Korean hackers are stepping up their attempts to steal bitcoin in order to support Kim Jong Un’s authoritarian regime.

Source::CNN