Social gaming developer Zynga has raised more than USD 15 million in funding, to add to the USD 40 million it raised in two previous funding drives last year.
Although the company has made no formal announcement, keeping the identity of the investors secret, an online SEC filing revealed the investment took place earlier this month.
Zynga is the largest of the social gaming developers, but also one of the more controversial - having been repeatedly accused of running scam promotions in its games.
Facebook has previously removed title FishVille from its pages as Zynga promised to remove all "Cost Per Action" offers until it could clean up its act.
Nevertheless, the company has an audience of almost 200 million for its titles, creating revenues of over USD 150 million. The firm is widely rumoured to be planning a public offering next year.
Recent weeks have seen a number of rival social gaming developers also gain significant funding, with Playdom raising USD 43 million, RockYou attracting USD 50 million in new investments and Playfish acquired by EA for USD 300 million.