Game of Thrones fans have been eagerly awaiting the fifth season which is due to start tonight on US television network HBO.
However, Mashable has reported that the first four episodes of the new series have been leaked online.
A spokesperson told the site: “Sadly, it seems the leaked four episodes of the upcoming season of Game of Thrones originated from within a group approved by HBO to receive them.
We’re actively assessing how this breach occurred”.
According to reports, the episodes were downloaded more than 100,000 times within the first three hours of them appearing online.
The New York Daily News reports that download numbers are expected to go into the million bracket by the end of the weekend.
GOT was the most pirated show of 2014 and this looks set to continue for 2015.