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 the lengthy investigation by Japanese police emerge, at least one crucial question remains unanswered: Where's the money?

The authorities issued a fresh arrest warrant for Frenchman Karpeles on Friday over claims he stole several million dollars from clients, including about $48,000 allegedly spent on a luxury canopy bed.