Two former allies of Gov. Chris Christie have been indicted on charges related to their alleged role in creating politically motivated traffic jams on the George Washington Bridge in 2013, and one has pleaded guilty to conspiracy charges in connection with the case.

An indictment against Bridget Kelly and Bill Baroni was unsealed Friday just hours after the former Port Authority official who resigned amid the political uproar over the 2013 bridge lane closures admitted in federal court in Newark that the three of them engaged in the plot as political retribution against the mayor of Fort Lee, where the entrance of the bridge is located.

David Wildstein, a former ally of Christie and a Christie appointee to the Port Authority, also admitted that the traffic study they initially said prompted the closures was meant to cover up the conspiracy.

The trio hatched the scheme in the summer but waited until the first day of school to "ratchet up the injury to Fort Lee residents," U.S. Attorney Paul Fishman said while announcing the charges.

The Christie allies responded with "radio silence" despite being told by Fort Lee Mayor Mark Sokolich that traffic was making students late for school and hampering first responders, Fishman said.

"Even when Mayor Sokolich warned that the lane reductions were compromising public safety neither Baroni nor Kelly nor Wildstein bothered to even ask Mayor Sokolich about the nature of those risks," Fishman said. "Instead they just kept the scheme going for as long as they could."

Kelly, who was fired by Christie as his deputy chief of staff after the plot came to light, and Baroni, who resigned from his job as deputy executive director of the Port Authority, are charged with nine counts including conspiracy and fraud. They are set to be arraigned Monday.

Baroni's attorney, Michael Baldasarre, told reporters Friday that the accusations against Baroni are false, calling Wildstein a habitual liar. 

"If David Wildstein was willing to repeatedly lie to settle a petty political grudge, no one should be surprised at his eagerness to concoct any story that he thinks will help him stay out of federal prison," he said. 

At a news briefing Friday, a defiant Kelly said after 16 months of silence on the matter of the closures she would no longer "let the lies that have been said about me go unchallenged." 

"I am not guilty of these charges," Kelly said. "I never ordered or conspired with David Wildstein to close or realign lanes at the bridge for any reason, much less retribution."

She said she doesn't know the mayor of Fort Lee and certainly harbors no ill will toward him.

"David Wildstein is a liar," Kelly said.

Christie was not implicated in the scandal, which skewered the Republican's presidential ambitions and caused his popularity in the Garden State to tank. Prosecutors said Friday based on the evidence they did not expect to charge anyone else in connection with the lane closures.

In a series of tweets, Christie said the indictments and guilty plea prove that he "had no knowledge or involvement in the planning or execution of this act."

"The moment I first learned of this unacceptable behavior I took action, firing staff believed to be accountable, calling for an outside investigation and agreeing to fully cooperate with all appropriate investigations, which I have done," he said on Twitter. "Now 15 months later it is time to let the justice system do its job."

Christie declined comment Friday morning as he left a hotel in McLean, Virginia, after speaking at a technology breakfast. Officials familiar with the nearly yearlong investigation have told NBC 4 New York that there is no evidence showing Christie had any advance knowledge of the lane closures.

Wildstein's lawyer, Alan Zegas, alleged in February 2014 that the governor knew about the lane closures and that he had evidence tying the governor to it.

Zegas reiterated the statement after his client pleaded guilty in court Friday, telling reporters, "Mr. Christie knew of the lane closures while they were occurring, and evidence exists to establish that." 

In Newark federal court before the indictments were unsealed, Wildstein pleaded guilty to two counts of conspiracy -- one for violating the civil rights of the people of Fort Lee who were affected by the traffic jam, and one for misuse of property by an agency that receives federal funds.

Wearing a dark suit, a significantly slimmed down Wildstein told a judge the intent of the lane closures of the bridge was political retribution against Sokolich, a Democrat, for failing to endorse Christie's gubernatorial re-election bid.

Asked if he and the other former Christie allies purposefully picked the first day of school to initiate the lane closures, knowing that would exacerbate the traffic problems, Wildstein said, "Yes." He also admitted ignoring the Fort Lee mayor's call for help.

Three local access lanes were cut to one for five days starting the morning of Monday, Sept. 9, 2013. The unannounced closings caused traffic backups that lasted hours on streets in Fort Lee, making children late for school and commuters late for school. It delayed emergency response.

Wildstein waived his right to indictment and will be sentenced in early August; it's not clear how much time he faces as part of the plea deal. Prosecutors said the 53-year-old was released on a personal recognizance bond of $100,000 and had to surrender his passport.

Prosecutors say Wildstein has been cooperating with their investigation and signed a plea agreement in January.

Zegas said his client has answered hundreds if not thousands of questions in connection with the case and fully accepts responsibility for his conduct. He said Wildstein deeply regrets his involvement in the lane closures and will testify at trial if necessary.

In email exchanges obtained by news outlets last year, Wildstein and Kelly wrote about shutting down the bridge.

"Time for some traffic problems in Fort Lee," Kelly wrote.

A few weeks later, on the weekend before the lane closures, Wildstein wrote to her: "I will call you Monday AM to let you know how Fort Lee goes."

Text messages also obtained by NBC 4 New York and other news outlets show an unidentified person texting Wildstein about Sokolich, asking for help on the second day of the closures: "Is it wrong that I am smiling?"

He texted back: "No."

The other person texted about feeling bad for children not being able to get to school because of the traffic.

Wildstein wrote back: "They are the children of Buono voters," referring to Christie's 2013 opponent for governor, Democrat Barbara Buono.

When asked Friday what Kelly meant when she texted "Time for some traffic problems," her attorney Michael Critchley Sr. said at a news conference: "That answer to that question will be given, and it will be given at a trial."

He added that the indictment rested on Wildstein's testimony, which he called unreliable and inaccurate. 

"What David Wildstein has done is cherry pick some facts, taken other facts out of context and ommitted other facts," said Critchley. They put together that out-of-context content and tried to make an indictment out of it." 

Assemblyman John Wisniewski, co-chair of the joint legislative panel tasked with investigating the lane closures, called the conspiracy on the first day of school "sickening."

"It's a sad day. They abused that trust so terribly," Wisniewski said.

Mayor Sokolich said Friday "it was a punch in the gut to me, to hear an individual plead guilty and subject himself to a potential jail term for conducting himself in an intentional way to get to me, and that way was teh partial closure of the busiest bridge in the world." 

He added, "To wait till the first day of school suggests to me it truly was venomous act, a calculated act and a despicable act."

In December, a 136-page interim report by that legislative panel found no evidence Christie was involved in the scheme. The report echoed the findings of an independent investigation commissioned by Christie's administration that found no proof the governor was involved in the closures or subsequent cover-up, and the governor has consistently denied any advance knowledge of the traffic scheme.

Federal prosecutors issued a new subpoena to the Port Authority last month in connection with the case seeking evidence related to claims that members of the Christie administration may have engaged in retaliatory action against Jersey City's mayor for the non-endorsement. The request included records from former Port Authority officials who were appointed by or were allies of Christie.

In a statement Friday, the Port Authority said it was continuing its practice of not commenting on the proceedings in the bridge case, but that it has worked for more than a year to rebuild the public's trust through reform and a renewed focus on its core mission.

"There is more to be done, and we will continue to make the necessary changes to transform the Port Authority into a more open and accountable organization that the region deserves," the agency's statement said. "We are in the process of reviewing the indictments to ascertain what additional steps, if any, we can take to prevent a recurrence of this type of abuse."