LONDON — “Big Brother” producer Endemol is to invest $13 million in social casino gaming company Plumbee. The digital start-up’s existing investor, Idinvest Partners, has also pumped in new coin. The deal values the business at $40 million.

Plumbee is a fast-expanding business that creates, operates and markets free-to-play online and mobile games on social networks such as Facebook.

The two companies will create premium social casino games, exploiting Endemol’s global entertainment brands and building on Plumbee’s worldwide user base.

Since launching in October 2011, Plumbee’s rapid growth has been driven by successes such as its flagship game “Mirrorball Slots,” which launched online and on iOS in July 2013, and is coming soon on Android. It is among the top 10 highest grossing social casino games on Facebook.

Social casino games are free to play, but players can purchase virtual credits in order to unlock more features and get upgrades, gifts, bonuses and more.

Plumbee also has a joint venture with leading online gambling company Unibet, called Bonza Gaming. The j.v. is behind “Bonza Slots,” one of the first ever real-money casino games on Facebook; and more recently has launched “Bonza Casino.”

London-based Plumbee, which was co-founded by CEO Raf Keustermans, chief operating officer Gerald Tan and chief technology officer Jodi Moran, employs more than 50 people, including designers, engineers, product managers, analysts and marketers.

Lucas Church, chair of Endemol’s Group commercial board, commented: “Social casino gaming is a fast-emerging market and Plumbee is one of the most innovative and dynamic operators in this space. This new partnership will allow us to accelerate the growth of Endemol’s digital gaming business around the world, whilst capturing more of the value created by our entertainment brands.”

Endemol’s digital gaming projects include a new initiative to move into app publishing, launching with gaming apps based on hit shows “Pointless” and “Deal or No Deal.” Recent successes include “The Money Drop” second screen game, which has so far had more than 30 million games played worldwide; “The Million Pound Drop” app in the U.K., which has had more than 2.5 million downloads to date; and a multitude of online and mobile games around the world for the company’s global brands such as “Big Brother.”

Plumbee was advised on the investment by Ingenious Corporate Finance.