Social network game developer, Zynga, who has achieved great success over the past few years with its highly popular free-to-play games, such as Farmville and Mafia Wars, is now smack bang in the centre of a Facebook identity-theft scandal.

According to a Wall Street Journal investigation, personal information from millions of Facebook users using particular applications has been leaked to at least 25 advertising companies. Users who play the following Zynga games may be affected: FarmVille, Texas HoldEm, Café World, Mafia Wars, Treasure Isle and FrontierVille.

Zynga has said that it doesn’t have any knowledge of how the identity leaks happened and a spokesperson for the company said it will be looking at ways to prevent it happening in the future.

"Zynga has a strict policy of not passing personally identifiable information to any third parties. We look forward to working with Facebook to refine how web technologies work to keep people in control of their information," reads the statement.

It’s not just Zynga’s games that are in the spotlight either. A number of other offending applications have disappeared from Facebook, though it’s interesting to see that Zynga, who have recently secured a $200m investment from Google, is still running all of the games involved in the scandal.

Facebook says that no private details were leaked, so there's no need for panic, but admits that user identities have inadvertently been given to advertising companies. Investigations continue.