(CNN) - Politically-embattled New Jersey Gov. Chris Christie's administration has retained a law firm to help conduct an internal review and cooperate with a U.S. Attorney inquiry into allegations top staffers orchestrated a traffic logjam in Fort Lee, New Jersey, as political payback.
The announcement comes on the same day a special state Assembly committee investigating the scandal plans on issuing subpoenas for documents as well as current and former aides, two sources familiar with the matter told CNN.
Documents released last week suggest members of Christie's inner circle ordered the closing of two access lanes to the George Washington Bridge in September, causing massive traffic problems for four days in Fort Lee, which serves as the access point to the bridge on the New Jersey side.
Former Deputy Chief of Staff Bridget Kelly, the governor's chief spokesman, Mike Drewniak, and Bill Stepien, a sharp-elbowed Christie political confidante who managed both his successful gubernatorial runs, are on the subpoena list, according to the sources.
Other names are also being discussed by the panel that is led by Democrats and will be assisted by attorney Reid Schar, a key figure in the federal prosecution of former Illinois Gov. Rod Blagojevich.
"Governor Christie made clear last week that he will conduct an internal review to uncover the facts surrounding the lane closures in Fort Lee," a statement from the governor's office read. "His administration is fully cooperating with the U.S. Attorney inquiry and other appropriate inquiries and requests for information."
The Christie administration has retained Gibson, Dunn & Crutcher LLP as outside counsel in a move the administration hopes "will bring an outside, third-party perspective to the situation."
Randy Mastro, a former Assistant United States Attorney for the Southern District of New York, will head up the legal team. Mastro has experience in organized crime cases and led the federal racketeering lawsuit that forced the International Brotherhood of Teamsters to hold democratic elections and to undergo court supervision. Mastro is also a former deputy mayor of New York City.
The pending legal showdown centers around whether the traffic gridlock was engineered as political retribution against the mayor of Fort Lee, who did not endorse Christie for re-election last November.
Christie has said he was stunned by the suggestion, which was first made by Democrats and subsequently magnified by explosive e-mails released last week by state legislators.
Christie fired Kelly. Her name appeared in e-mails with an appointee at the Port Authority of New York and New Jersey, David Wildstein, who left his job as the scandal unfolded last fall. One e-mail quoted her as saying: "Time for some traffic problems in Fort Lee."
On Tuesday, Christie addressed the scandal briefly in his State of the State address, saying that "mistakes were clearly made." He said previously, however, that he knew nothing about any notion of a deliberate attempt to tie up traffic, much less exact revenge on Sokolich.