Cryptocurrency exchange Binance, one of the world's largest, was hacked and about 7,000 bitcoin, valued at more than $40 million, were stolen.

"We have discovered a large scale security breach today, May 7, 2019 at 17:15:24 (UTC). Hackers were able to obtain a large number of user API keys, 2FA codes, and potentially other info. The hackers used a variety of techniques, including phishing, viruses and other attacks. We are still concluding all possible methods used. There may also be additional affected accounts that have not been identified yet," Binance said in a statement on its website.

"The hackers had the patience to wait, and execute well-orchestrated actions through multiple seemingly independent accounts at the most opportune time," Binance said."The transaction is structured in a way that passed our existing security checks. It was unfortunate that we were not able to block this withdrawal before it was executed. Once executed, the withdrawal triggered various alarms in our system. We stopped all withdrawals immediately after that."

Binance said it would cover the incident in full and "no user funds will be affected."

Bitcoin has surged this week, topping $5,900 on Tuesday before falling slightly.

The cryptocurrency has risen about 3% this week and has gained close to 20% since April 1, when a private investor reportedly purchased $100 million in cryptocurrency.