As expected, Deus Ex 3 developer Eidos Montreal today announced its second title, Thief 4, referring to the oft-rumored project as "the worst kept secret in the industry."

Few details on the stealth-action sequel were given--no word on specific platforms or a release estimate--with Eidos Montreal general manager Stephane D'Astous stating that it is "in the early development stages."

While today's announcement referred to the title as "Thief 4," the game's official website uses the "THI4F" graphic displayed above.

"It's too early for us to offer any specific game details, right now we are focused on recruiting the very best talent to join the core team at the studio and help us make what we believe will be one of the most exciting games on the market," D'Astous continued.

Word that Eidos Montreal is set to announce its second project has lead forum-goers to deduce that the title is likely the fourth entry to the company's revered series of stealth-action games, Thief.

Following its announcement of Deus Ex 3, Eidos last year hinted that the title of its second unannounced game begins with the letter "T"--prompting quick assumptions of Thief 4.

But according to a recent advertisement in Edge magazine, the upcoming title also resides on GameSpot's "Hall of Fame," "Greatest Games of All Time" and "Ten Best Heroes of Gaming" lists. As Kotaku points out, GameSpot forum members soon realized that Thief is the only game mentioned on all three lists.

Eidos Montreal is predictably declining to comment on the rumors, instead pointing to May 11 as the day it will officially reveal the project.