When Half Life: Episode 3 concept art surfaced on the facebook page of fansite ValveTime yesterday we were sceptical, but it's increasingly appearing that they really could be from the long awaited sequel.

Most of the artwork depicts a snowy wilderness with characters clad in winter clothing. This tallies with location the Borealis, the Aperture science ship that was revealed to be stranded in the Arctic in Episode Two. More intriguingly several of the stranger pieces of artwork contain the word 'Xen' in the file names, the Alien world visited in the original Half Life's final act.

OXM have been on top of the story and note that moderators on the Steam forums are claiming the pictures are genuine. Meanwhile fansite Lambda Generation traced the images back to a (since deleted) Picasa gallery belonging to Valve artist Andrea Wicklund.

Now here's the bad news. Although they were only recently discovered these images were all uploaded to Picasa in March 2008, only a few months after the release of Episode Two. This means that even if they are genuine, they aren't necessarily indicative of the direction Valve are taking now, four years later.

You can see the full gallery of images over at Valve Time .