Valve have announced new downloadable content for Left 4 Dead 2 named Cold Stream.

The add-on is a work-in-progress and has been created by a community member named Matthew Lourdelet, who made such a splash with Valve they requested his mod be completed and worked into their next DLC release. The developer wants the help of the community.

"The very first step in creating a new DLC is deciding on the larger goals and constraints for the DLC," wrote Valve on the Left 4 Dead blog.

"The Sacrifice and the Passing were story heavy, so we want to see what the other end of the spectrum looks like. For this DLC we start with wanting to experiment by releasing a map pack that wasn't about story. It would just be new campaigns for Left 4 Dead 2."

So there’s to be no new story as such, but the pack will have three remaining L4D1 campaigns along with Cold Stream.

"That's the start of the DLC," Valve added. "We have the basic information but we don't even have a name or release date yet."

It should apparently be out "sometime after Portal 2" and will come out on the Mac, PC and Xbox 360.

"In the next few weeks we will add Cold Stream to the UI (user interface) and we will all begin testing it," Valve said. "As we receive feedback and test data we will also share some data we collect on player experience and show how we put that data to use.

"While the beta will only be available for PC and Mac users, we appreciate feedback and ideas from the entire community. This is an experiment for us, so please let us know what you think and what you would like to see in the DLC – just remember the constraints."

If you’d like more on the game, check out the Left 4 Dead 2 hub.