NEW YORK (AP) — Gov. Chris Christie was not involved in a plot to create gridlock near a major bridge in a scheme directed at a mayor, lawyers hired by the administration reported Thursday while also defending the integrity of their internal review amid separate federal and legislative investigations.

The taxpayer-funded report released by former federal prosecutor Randy Mastro relied on interviews with Christie and other officials in his administration and 250,000 documents, many of them emails and text messages. But the key figures in the plot would not cooperate with Mastro's investigation, leading Democrats to question the credibility of the report and its thoroughness.

The investigation concluded Christie had no knowledge beforehand of lane closings in September near the George Washington Bridge between New Jersey and New York that caused four days of massive gridlock in the community of Fort Lee.

The closings became a major scandal for the governor in January when he had to backtrack and acknowledge the involvement of a top aide and an associate in orchestrating the closings. He has repeatedly denied knowing about the plot or having any involvement in the closings.

"Governor Christie's account of these events rings true. It's corroborated by many witnesses, and he has conducted himself at every turn as someone who has nothing to hide," the report found.

"We uncovered nothing contradicting the governor's account," it concluded.

The report did not find even minor missteps by Christie and his inner circle. It cast Christie as a leader was deeply troubled about the possibility that staff members were not being truthful to him — asking "with tears in his eyes" whether any of his top aides were involved in the lane closure.

During a news conference, Mastro emphasized that the review found no evidence that the scheme was reflective of the wider operations of the governor's office.

"We found that this was the action of the few," he said. "This is not reflective of the whole."

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On a radio show Wednesday night, Christie, a possible 2016 Republican presidential contender, said the events of the past several months will not affect his decisions about his political future.

Mastro's report comes out ahead of results from independent investigations by federal prosecutors and a special committee of state lawmakers.

Defending the report, Mastro said his team was able to review a trove of documents, including emails and text messages among Christie, Lt. Gov. Kim Guadagno, top governor's office staff and former staffers.

"We believe we have gotten to the truth or we wouldn't be reporting it," he said.

He also said his team was sharing information with federal prosecutors.

The report, issued at Mastro's New York law office, concluded that former Port Authority of New York and New Jersey official David Wildstein and ex-Christie aide Bridget Kelly were behind the closures and that they were targeting Fort Lee Mayor Mark Sokolich.

It did not determine why they wanted to hurt the Democrat yet said there was no evidence that it was because he refused to endorse Christie for re-election last year.

The report said that Sokolich himself brought up the possibility of endorsing Christie but ultimately decided against it. The report said that even after that decision, the mayor remained on a list of Democrats whom Christie was considering appointing to various boards.

Both Wildstein and Kelly have refused to talk to investigators, citing their right against self-incrimination. The report delved into their personalities.

"Whatever motivated Wildstein and Kelly to act as they did, it was not at the behest of Governor Christie, who knew nothing about it," the report said.

Mastro said Wildstein seemed to have "bizarre political and personal animus" against a variety of people. He also quotes another Christie confidante as saying Wildstein had "50 crazy ideas a week."

The report said Kelly tried to cover her tracks when Christie began asking what happened last year. She asked a colleague to delete an email about the plot, but the other staffer retained the email anyway, the report said.

The report also suggested Kelly may have been motivated to participate in part because she'd recently been dumped in a romantic relationship by a former Christie campaign manager.

Christie also cut ties in January with that strategist, Bill Stepien, over the scandal. The report finds that he knew about the lane closures but not about an ulterior motive. His lawyer, Kevin Marino, said Thursday that raises the question of why Stepien was ousted from Christie's realm. "I just wish someone would acknowledge it was a mistake," said Marino, who also said the mentioning of Stepien's relationship with Kelly, when both were single and not working together, was gratuitous.

Lawyers for Kelly and Wildstein did not return messages.

Mastro said Wildstein suggested he mentioned traffic issues in Fort Lee to Christie at public event during the lane closures. But he says Christie did not recall it being brought up and if it was, it would not have registered as significant to Christie — something Christie has said before.

In a separate investigation, the report found that a claim by Hoboken Mayor Dawn Zimmer, that Christie's administration told her that Superstorm Sandy would be tied to a private redevelopment plan, is "demonstrably false." In response, Zimmer called the report "sadly predictable" and a "one-sided whitewash."

Mastro called for Christie's office staffers to cease using personal email accounts for official business, eliminating the office where Kelly had worked and appointing an ethics officer in the governor's office. He also recommended major changes to the structure of Port Authority, an agency jointly run by the states of New York and New Jersey.

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Mulvihill reported from Trenton, N.J. AP writer David Porter in Newark, N.J., also contributed.