By Jeremy Wagstaff SINGAPORE (Reuters) – Criminals may already have made off with up to $500 million worth of bitcoins since the virtual currency launched in 2009 – and you can double that if it turns out they emptied Mt. Gox. “It's just growing pains,” says Keith Jarvis, a security researcher at Dell SecureWorks. “Bitcoin is large enough and has enough momentum behind it to survive any public relations damage from this (Mt. Gox) case or anything else.” The fall of Mt Gox, the Tokyo-based exchange which filed for bankruptcy last month after saying it lost some 850,000 bitcoins to hackers, is certainly the virtual currency's biggest crisis. But data collated by Reuters from specialist bitcoin industry websites and internet forums shows that more than 730,000 bitcoins were already missing to theft, hacking, cyber-ransom payments and other apparently criminal pursuits before Mt. Gox's collapse.