The US Justice Department said Thursday it has launched an antitrust probe of the mega merger of Comcast and Time Warner Cable.
The $45.2 billion tie-up would unite the largest US cable companies, which also are among the largest broadband Internet providers.
Justice Department spokeswoman Gina Talamona said the agency's antitrust division "is looking at the proposed acquisition involving Comcast and Time Warner."
She said in a statement that Assistant Attorney General Bill Baer would be recused and that "the investigation will be overseen by two experienced antitrust practitioners," principal deputy assistant attorney general Renata Hesse and deputy assistant attorney general David Gelfand.
The deal announced last month raised concerns about the reach of Comcast, which owns NBCUniversal's film and television assets and is one of the largest providers of cable Internet.
Even with a planned divestment, the merger would create a colossus with 30 million customers and some 30 percent of the US pay television market.
The companies said the deal would save $1.5 billion in operating costs and help facilitate the deployment of new technologies for video and Internet.
Backers of the deal claim Comcast and other cable firms are positioning themselves for a new landscape and competing against services like Netflix and telecom operators such as AT&T and Verizon, which offer packages of services to those of Comcast.
Analysts have said regulators would carefully scrutinize the deal, not only due to the creation of a dominant cable television operator but because of Comcast's ownership of one of the major television networks and Hollywood studios.
Comcast, in acquiring NBCU, agreed to abide by so-called net neutrality rules that bar discrimination against competing online services.
But Comcast raised eyebrows last month with a separate deal with Netflix in which the streaming video service would pay for smoother delivery, which could set a precedent for other online services.