The arrest of MtGox boss Mark Karpeles has begun to shed light on the defunct Bitcoin exchange after hundreds of millions of dollars in virtual currency vanished from its digital vaults last year. But as details of a lengthy investigation by Japanese police trickle out, at least one crucial question remains unanswered: where is the money? On Friday authorities issued a fresh arrest warrant for Frenchman Karpeles over claims he stole several million dollars from clients, including about $48,000 allegedly spent on a luxury canopy bed. Karpeles, 30, who has reportedly denied the allegations, was initially taken into custody earlier this month and has been held without formal charges for three weeks, as allowed under Japanese law. A fresh warrant resets the clock on how long police can hold him and grill the self-described computer geek over Tokyo-based MtGox's missing Bitcoins. So far, police have accused Karpeles of manipulating data and stealing sums that amount to just a fraction of the 850,000 coins - worth around $480 million at the time, or $387 million at current exchange rates - that disappeared last year.Karpeles claimed he had found some 200,000 of the lost coins in a "cold wallet" - a storage device, such as a memory stick, that is not connected to other computers. But the whereabouts of the money and Karpeles' involvement appear far from solved. MtGox reportedly kept its own funds and clients' money in the same bank account. Investors have called on the firm's court-appointed administrators to publicize its data so that experts around the world can help analyze what happened at MtGox.