A number of videos have appeared on YouTube showcasing unreleased footage of Gears of War 3's campaign mode.
The videos have prompted Microsoft to investigate how the videos were made, with all signs pointing to a leaked copy of the game making its way online.
"We have seen the reports of Gears of War 3 content being propped on the Web and working closely with our security teams and law enforcement to address the situation," Microsoft said in a statement given to IGN.
"This content is not from a final build and is not representative of what fans will enjoy when the game launches."
Have you got your hands on this leaked version of Gears of War 3?