Bitstamp had suspended its service after the breach resulted in the loss of around 19,000 bitcoins with a value of some $5 million. "Trading will resume during the day today," Damijan Merlak, one of Bitstamp's two Slovenian founders, told Reuters in an emailed message on Friday.

On Wednesday Bitstamp had said it expected that trading could resume within 24 hours and added that customers would not lose money because of the breach and that security would be increased. Merlak said various institutions from the European Union and the United States were investigating the security breach without naming them. The Slovenian police told Reuters it was not involved in the investigation.

Last February, Bitstamp claimed that developers had come up with a solution to thwart cyber attacks against its platform after Mt. Gox, once the world's biggest bitcoin exchanges, lost an estimated $650 million worth of the virtual currency when its computer system was hacked.

The Bitstamp breach represented a small fraction of its total bitcoin reserve and the majority was held in secure offline systems, the Slovenia-based firm posted on its website. Bitcoin, the best-known virtual currency, started circulating in 2009. Unlike conventional money, bitcoin is generated by computers and is independent of control or backing by any government. A bitcoin is currently worth $276.80.

Merlak, 28, and his colleague Nejc Kodric, 25, both computer experts, founded Bitstamp in 2011. According to the Slovenian media the two had earned about 23 million euros ($27.2 million) from the enterprise which places them among the 50 richest Slovenians.

Reuters