Michael Drewniak is not a target of the investigation but was in federal court to answer questions, his attorney Anthony Iacullo told ABC News. Iacullo declined to say what was discussed before the grand jury, but told the TV news program that he received assurances his client would be considered a witness throughout the proceedings.
US Attorney spokeswoman Rebekah Carmichael said she could not comment on the ongoing investigation.
Drewniak and Iacullo did not return phone messages Friday.
Former Christie aides allegedly ordered the closing of two traffic lanes near the George Washington Bridge last September, resulting in gridlock in the nearby town of Fort Lee to retaliate against the mayor, a Democrat who did not endorse Christie in his November re-election bid.
The governor maintains he knew nothing about the scheme in advance or while the lanes were closed for four days. A report by lawyers he commissioned backs up his claim. He has referred to the lane closings as "inexplicably stupid."
However, the investigation by U.S. Attorney Paul Fishman and a parallel probe by a state legislative panel are ongoing.
Drewniak, who has been Christie's press secretary since Christie's days as U.S. attorney in New Jersey before becoming governor in 2009, received emails about the traffic-blocking plot after it was carried out. He also drafted a resignation letter that Christie edited for another key figure, David Wildstein, who is said to have thought up the lane-blocking scheme.
Lawyers for Bridget Kelly and Bill Stepien, two former Christie associates who are key figures in the scandal, said their clients have not been called to testify before the federal grand jury. A lawyer for Bill Baroni, a former Christie deputy with the agency that runs the bridge, refused to comment.
The legislative panel will meet next week to vote on issuing subpoenas for the interviews Christie's lawyers used as the basis for clearing the governor. A judge's ruling is also expected soon on whether Kelly and Stepien will be required to turn over documents to the legislative investigators involving the lane closings.
Kelly and Stepien are fighting to have subpoenas withdrawn by asserting their Fifth Amendment right against self-incrimination. Most of the people and organizations close to Christie that have received subpoenas are handing over the requested documents.