 -- Gov. Chris Christie, a potential presidential contender, was interrogated recently by federal investigators probing the 2013 lane-closure scandal that has threatened his political future, officials confirmed to ABC News.

Christie met with federal prosecutors and FBI agents last month during a secret session at the New Jersey governor’s mansion in Princeton. He agreed to sit down with investigators voluntarily after they offered him a chance to provide his side of the story. Interviewing Christie was one of the final steps in the investigation, which appears to be wrapping up, according to those briefed on it.

Anyone being questioned by federal agents is required to tell to the truth or potentially face criminal charges. The governor was accompanied by his personal attorney, Christopher Wray, a former chief of the Justice Department’s Criminal Division.

Christie Cleared--Sort of--in Bridge Scandal

“Governor Christie made clear from day one that he and his administration would fully cooperate with all appropriate inquiries,” Christie spokeswoman Maria Comella told ABC News. “That’s exactly what he has done and will continue to do, and he is very much looking forward to this matter’s conclusion.”

US Attorney Paul Fishman, who’s leading the investigation, declined to comment on the meeting.

The New Jersey US Attorney’s Office and the FBI have spent a year investigating the September 2013 closing of access lanes at the George Washington Bridge, which caused unprecedented traffic jams for the better part of a week and crippled Fort Lee, where the GWB is anchored in New Jersey. It has been alleged that the lanes were closed as political payback for the Democratic mayor of Fort Lee after he declined to endorse Christie’s gubernatorial re-election in 2013, though Christie has repeatedly denied it.

The GWB lane scandal was simmering for much of late 2013, but only burst into national headlines a year ago Thursday when it was revealed that a deputy chief of staff to Christie, Bridget Kelly, had sent an email that appeared to green-light the closing of two out of three local-access lanes to the span – the most heavily traveled in the country. The bridge is operated by the Port Authority, which is controlled jointly by the governors of New Jersey and New York.

Kelly’s words – contained in emails submitted to a state legislature investigative committee – thrust Christie and his inner circle into a crisis first marked by a marathon Statehouse news conference and then two months of dodging questions on the incident. During the meeting with reporters a year ago today, Christie said, “I have nothing to hide. So any questions anybody wants to ask me, they can ask, you know. From law enforcement, you know, anything they want to ask, they can ask. So we have nothing to hide, and this administration has nothing to hide.”

Federal authorities offered Christie the opportunity to meet with them months ago, officials familiar with the case explained. The governor was slow to respond originally the feds, making authorities fear he might be ignoring the overtures. Prosecutors quietly considered whether to ratchet up the pressure by issuing a subpoena for the governor to appear before a federal grand jury, but then Christie’s camp made arrangements for the governor to meet with them after Election Day and at one of the most secluded places in New Jersey, the ornate executive mansion – known as Drumthwacket. Little of the 11-acre property is visible from outside the gates and the estate is secured by the NJ State Police. By contrast, the federal grand jury convened to investigate the GWB scandal meets weekly at a busy courthouse in downtown Newark.

Christie’s session with the feds was scheduled to last as long as the feds wanted. It went on for far more than two hours.

The meeting was termed “professional, collegial and courteous,” by someone familiar with what went on.

Being interviewed by the authorities was yet another ironic twist for Christie, who has gone from being a feared federal prosecutor famous for tormenting governors to being a governor himself probed by the feds. Little more than 10 years ago, while Christie was New Jersey’s US attorney, he dispatched federal agents to the governor’s mansion to interview then-Gov. Jim McGreevey, who had just resigned, saying he was being blackmailed by a former aide. This time, Christie was the one being questioned as prosecutors determine what happened at the GWB, who ordered it, whether any federal laws were broken and, if so, by whom.

Once Kelly’s email was revealed, Christie fired her instantly and cut ties with his former campaign manager, Bill Stepien, who had been widely viewed as the man who would run a Christie presidential campaign.

The governor also retained an outside law firm to investigate what came to be known as “Bridge-gate.” That effort, led by former New York City Deputy Mayor Randy Mastro, cleared the governor. The day Mastro’s report was released, Christie met with Diane Sawyer of ABC News and, in an exclusive interview, said he "did nothing to create the environment" that prompted his former top aides to shut down the lanes.

Though the Mastro report exonerated Christie, it had no effect on the other investigations spawned by GWB scandal, the most wide-ranging of which is the one being led by Fishman. As part of that probe, a federal grand jury spent weeks taking testimony from people on all sides of the case. In April, ABC News reported exclusively that longtime Christie press secretary Mike Drewniak appeared before the grand jury – as a “fact witness” -- for more than two hours to explain what he knows about the scandal.

Christie and his aides are also facing continued scrutiny from a series of other probes being conducted by the Manhattan DA’s office, the legislature and the Port Authority Inspector General. In addition, the results of the FBI probe could be turned over to state prosecutors in the event they want to file their own charges in connection with the lane closing.