According to a latest report released by a group investigating Mt Gox's case, the missing bitcoins were stolen from the exchange over a period of time starting from 2011. The report added that the bitcoins were gone much before the exchange's failure in February last year.
The company had been operating on fractional reserve basis for most of that time, either intentionally or unintentionally.
WizSec, a Tokyo-based bitcoin security company, has been unofficially investigating Mt Gox's collapse. Its report says its team has listed more than 2m bitcoin addresses linked to Mt Gox by matching leaked data with blockchain records and carrying out clustering analysis on addresses used at similar times.
