New Jersey Governor Chris Christie has said he is still looking into the possibility that other members of his staff were involved in the scandal over shutting down lanes onto the busy George Washington Bridge.
Christie said he will "take action" if it is needed.
New Jersey Governor Chris Christie said he has fired a top aide "because she lied to me".
Christie said the termination of Bridget Kelly's employment was "effective immediately".
Kelly had been Christie's deputy chief of staff for legislative and intergovernmental affairs.
New Jersey Governor Chris Christie said he is "embarrassed and humiliated" by conduct of some people on his team following a scandal over his staff's alleged role in shutting down lanes onto the busy George Washington Bridge to punish a mayor.
Christie said, "There is no doubt in my mind that the conduct that they exhibited is completely unacceptable and showed a lack of respect for the appropriate role of government and for the people that we are trusted to serve".
Christie, a possible Republican White House contender, held a news conference after he became enmeshed in the scandal.
The US attorney in New Jersey is set to open an inquiry into recent controversial bridge lane closures, which critics say were engineered by New Jersey Governor Chris Christie's staff for political retribution, The New York Times reported.
The newspaper gave no further details.
Christie is a possible Republican contender for the 2016 White House race.
A senior aide to New Jersey Governor Chris Christie deliberately created a traffic jam to punish a mayor, a series of emails and text messages revealed.
The messages, obtained yesterday by the Associated Press and others, came amid an investigation into whether a huge traffic backup last year was retribution against the mayor of Fort Lee for not endorsing Mr Christie for re-election last autumn.
Mr Chirstie's deputy chief of staff Bridget Anne Kelly wrote in a message to David Wildstein: "Time for some traffic problems in Fort Lee," to which Mr Wildstein, a Christie appointee on the Port Authority of New York and New Jersey, responded: "Got it."
A few weeks later, he closed two of three lanes connecting Fort Lee to the busy George Washington Bridge, which runs between New Jersey and New York City.
The messages do not directly implicate Mr Christie in the shutdown, who said he was "outraged and deeply saddened" by the incident.
The 2016 race for the White House has collected a likely candidate in Chris Christie, who appears primed to run for the US Presidency after his triumphant re-election as New Jersey Governor.
Gov. Christie said he is happy to "stubbornly" refuse to discuss his future ambitions, but few doubt he plans to sell his moderate Republicanism to a national audience.
But will he be a match for an experienced campaigner like Hillary Clinton, who remains hotly tipped to run again for the Democrats?
Washington Correspondent Robert Moore reports from New Jersey:
New Jersey Governor Chris Christie underwent lap band surgery in February to reduce the size of his stomach, a spokesman confirmed.
A prominent Republican seen as a possible 2016 contender for the White House, Christie told the New York Post that his decision to undergo the procedure - which limits the amount of food the stomach can hold - was motivated by his family's concern for his health and not political ambition.
"This is a hell of a lot more important to me than running for president," Christie, a father of four, said at a news conference in Newark. "This is about my family's future."
He added that he had planned to undergo the procedure last year but it had been delayed by a need to deal with Hurricane Sandy, which caused devastation in his state last October.
New Jersey Governor Chris Christie visited Moonachie, New Jersey, yesterday to survey the damage, telling residents their "sense of safety was violated" by Sandy.
Governor Christie thanked first responders and emergency crews for their efforts during the storm and their continued hard work during the aftermath.
Governor Christie told the crowd, "People feel an enormous sense of loss, there's nothing more precious to people than their homes. Homes are where their families are, the memories and possessions of their lives, and there's also a sense of safety at home".
"That sense of safety was violated on Monday ... with people having to literally swim, climb, jump for their lives," he added.