New Jersey Gov. Chris Christie speaks about his knowledge of a traffic study that snarled traffic at the George Washington Bridge during a news conference on Jan. 9, 2014 at the Statehouse in Trenton, New Jersey. Jeff Zelevansky/Getty Images

A former Port Authority official who oversaw the orchestration of lane closures on the George Washington Bridge last September — causing a traffic jam and a scandal that embroiled New Jersey Gov. Chris Christie — said Friday that the governor knew about the closures as they were happening and that he has the evidence to prove it.

Christie's office insisted Friday that the governor told the truth at a press conference earlier this month, in which he denied involvement in the incident, which appears to be an act of political revenge.

Former Port Authority official David Wildstein released a letter through his attorney Alan Zegas in which Wildstein describes the decision to close lanes as "the Christie administration's order."

Wildstein's letter went on to say that "evidence exists as well tying Mr. Christie to having knowledge of the lane closures during the period when the lanes were closed, contrary to what the governor stated publicly in a two-hour press conference" on Jan. 9 and earlier one on Dec. 13.

In the aftermath of the traffic jam, Christie, who is a Republican, has said on more than one occasion that he was told the lane closures were part of a traffic study, insisting that he was not aware of any political motivation.

The allegations that the lane closures were an act of revenge — to retaliate against Fort Lee Mayor Mark Sokolich, a Democrat, for not endorsing Christie for re-election — have complicated Christie's prospects of a presidential run in 2016.

But Christie's office reiterated Friday that the governor "had absolutely no prior knowledge of the lane closures before they happened and whatever Mr. Wildstein's motivations were for closing them to begin with."

"As the Governor said in a Dec. 13 press conference, he only first learned lanes were closed when it was reported by the press, and as he said in his Jan. 9 press conference, had no indication that this was anything other than a traffic study until he read otherwise the morning of Jan. 8."

On Friday night, Christie appeared at a birthday party for radio personality Howard Stern, but did not take questions after introducing a performance by Jon Bon Jovi.

In early January, the alleged plot by Christie's aides was exposed when documents were revealed showing that Bridget Anne Kelly, deputy chief of staff to Christie, had sent an email to Wildstein saying "time for some traffic problems in Fort Lee" — the town on the New Jersey side of the bridge.

Christie's aides had previously tried but failed to receive an endorsement from Mayor Sokolich.

Soon after the news broke, Christie fired Kelly, and Wildstein, then-director of interstate capital projects at the Port Authority, resigned.

New Jersey legislators are investigating whether Christie aides engineered the lane closures in the community of Fort Lee to send a message to the town's Democratic mayor. The U.S. Attorney's office is also investigating. Twenty subpoenas for documents and correspondence related to the lane closings are due to be returned to the legislative panel Monday.

No subpoenas target Christie himself, who has just begun a yearlong chairmanship of the Republican Governors Association.

Matt Arco, of Politicker NJ, a news website, told Al Jazeera that "Wildstein had testified in front of a committee of the legislature looking into this, and he took the fifth ... he didn't really discuss anything at all."

Wildstein's lawyer has suggested that he will talk if offered immunity.

"This suggests Wildstein has a story to tell and maybe we're going to be hearing more from him," Arco said. "There must be more emails or text messages."

Arco, who was at the early January press conference where Christie vehemently denied any prior knowledge of the closures, said the governor "was emphatic about how this was new information, and he didn't know about the lane closures."

"He was quick to terminate the one official he said had lied to him, and then distanced himself from the others," Arco said. "But it's important not to rush to judgment."

The bridge scandal could have big implications for Christie's future political career, as he has been considered a front-runner in the 2016 presidential elections.

Michael Shure, a political contributor for Al Jazeera, said Christie's chances of winning the Republican nomination for president in 2016 were already tarnished even before the latest revelations.

"If this turns out to be thuggery and revenge ... then he has to worry about keeping his current job, not even thinking about his next job," Shure said.

Al Jazeera and The Associated Press