Communications group Cox Enterprises Inc. has acquired Providence Equity Partners’ interest in AutoTrader Group. Sources tell Mergers & Acquisitions the price is $1.8 billion.

The additional 25 percent stake brings Cox’s ownership in AutoTrader to 98 percent. Current and former employees hold the remainder of the company.

AutoTrader operates AutoTrader.com and KBB.com, which provide online automotive marketplaces as well as marketing and software programs for car dealers.

Private equity firm Providence Equity, headquartered in Providence, R.I., bought a 25 percent stake in the company in 2010. Since then, AutoTrader has acquired Haystak Digital Marketing, HomeNet Automotive, Kelley Blue Book, vAuto and VinSolutions, which are all now part of AutoTrader Group. Providence is also invested in Chermin Group, Education Management Corp. and Trilogy International Partners. The deal provided a three times return to Providence. AutoTrader also paid a $100 million dividend to Providence in 2012, according to a source.

Cox, headquartered in Atlanta, also owns Manheim, a provider of vehicle marketing services.