Intrepid players have discovered that Team Fortress 2‘s most recent update contains references to an invasion and UFOs, the latter of which have now begun popping up in Valve’s popular shooter.

The update notes don’t specifically call out any of this, but the company appears to be readying a new event. I joined a Valve server on the map 2Fort this afternoon and found several posters scattered around the map, as well as a UFO hovering in the distance. You can check out some screenshots below.

Members of the Facepunch forums claim the UFOs and posters have popped up on other maps, too. User DevinWatson reports that there the code also contains new assets related to “update_invasion,” including posters and UFOs.

What purpose these serve beyond window dressing is unclear; at the moment, it’s likely just a tease of something to come. TF2 traditionally has some kind of event to celebrate Halloween (such as 2010’s Horseless Headless Horsemann), and it’s possible this year’s will center around UFOs. It could also just be that someone at Valve is excited for the return of The X-Files, considering the “I Want to Believe” poster referencing the show.

Valve has yet to make any formal announcements regarding the UFOs, though a trailer for something called the Invasion Update did leak earlier this year. We’ll keep an eye out for the official word on what’s happening.