Rumor has it that the eagerly anticipated "Left 4 Dead 3" game is currently under development. Recently, a new reference to the unannounced third installment in the co-op zombie-killing series was found in a Valve employee's development tutorial.

Though "Left 4 Dead 3" has not been officially announced, the leaked image hinted that Valve has been working on the new game under the radar.

A Valve fansite, ValveTime, posted a screenshot taken from a development tutorial by Valve artist Tristan Reidford for Destinations Workshop Tools. In the screenshot, a folder named "left4dead3" is noticeable.

Interestingly, the image was quickly supplanted with a new image, which only shows Reidford's default folders. However, a slew of screenshots was said to be taken before the said image was brought down.

The leaked image has lead to much speculations, claiming that the third installment is now underway at Valve Software. Although Valve did not give any official statement about the rumored project amid this year's Electronic Entertainment Expo (E3), it is strongly predicted that "Left 4 Dead 3" will have an enhanced gameplay setting, four new characters, more extensive map selection, and six separate campaigns.

According to Express Gaming, the four new characters have already been given names. The sole female character is said to be known as Katherine, while the three male characters are as follows: comic book geek Keenan, renowned Kenpo fighter Garrett Jr., and a gangster named Irvin.

Developed by Valve South, "Left 4 Dead" is set during the aftermath of an apocalyptic pandemic. The cooperative first-person shooter video game pits its four heroes, dubbed the Survivors, against hordes of the infected individuals.

The release date for "Left 4 Dead 3" has not been revealed as of writing, though the game is expected to arrive sometime in 2017. Stay tuned for more news and updates.