A recent job listing for a senior engineer stated that experience developing with the engine would be beneficial.
The main jobs listing adds that the Dundee-based studio is working on "a number of projects".
Meanwhile, lead level designer Sean Noonan's LinkedIn page shows up to four unannounced projects at the studio in the works since early 2011, including a third-person action title and a multiplayer game, with further mentions of CryEngine 3.
Formed by former Realtime Worlds members, Ruffian Games released Xbox 360 exclusive Crackdown 2 in 2010.
The studio told Digital Spy that it would "love" to work on another Crackdown game.
TimeSplitters 4, which is expected to use CryEngine 3, was rumoured to be in development last year.
> Read our review of Crackdown 2
Watch a trailer for Crackdown 2's Deluge DLC below: