(CNN) - David Wildstein, a central figure in a political scandal that has upended the administration of New Jersey Gov. Chris Christie, met recently with federal prosecutors, two U.S. officials familiar with the matter told CNN.
The U.S. attorney's office in Newark is investigating suggestions that top Christie appointees and allies orchestrated traffic tie-ups near the George Washington Bridge in Fort Lee last September.
Prosecutors are looking at whether the gridlock was politically motivated.
A state legislative committee is also investigating the matter, which involved sudden closures of access lanes to the nation's busiest bridge over several days.
Separately, one U.S. official said lawyers from the Justice Department's public integrity section have joined the investigation to consult on certain legal aspects.
This particularly involves separate allegations the Christie administration conditioned Superstorm Sandy relief money for Hoboken on its mayor's support for a redevelopment project backed by the governor.
State officials deny the assertion leveled by Hoboken's mayor, Dawn Zimmer.
The federal government has provided billions in aid money following the historic 2012 storm that ravaged parts of the Jersey Shore.
A Christie appointee, Wildstein at the time was a top executive at the Port Authority of New York and New Jersey, which oversees the bridge.
The federal officials said Wildstein, also a former high school classmate of Christie, met with prosecutors in Newark for an interview.
The office of U.S. Attorney Paul Fishman declined to comment.
Wildstein's attorney, Alan Zegas, did not respond to requests for comment.
He has previously said his client would be more inclined to tell investigators what he knew about the orchestrated traffic jams if he received immunity from prosecution.
One of the officials, neither of whom spoke to CNN for full attribution, said no immunity has been offered to any witnesses in the scandal that has called into question Christie's forceful governing style and clouded his potential presidential prospects.
Wildstein resigned from his job in December as the traffic scandal intensified.
An internal report conducted by outside lawyers hired by Christie's office concluded last month that Wildstein carried out the lane closures, and told another state official that he informed Christie about it at the time.
Christie has denied knowing anything about the gridlock until after it happened, and has said he knew nothing about any political mischief by members of his administration.
The internal investigation, summed up in a report by the legal team, also said Christie did "not recall" any conversation with Wildstein about it.
Wildstein was on the receiving end of text messages from another former top Christie aide in Trenton, Bridget Anne Kelly, who is said to have sent the infamous communication weeks before the tie-ups: "Time for some traffic problems in Fort Lee."
CNN’s Evan Perez and Steve Kastenbaum contributed to this report.