Gov. Chris Christie and an erstwhile ally are split on a question that has lingered since lane closures at the George Washington Bridge plunged his administration into scandal, a new report shows.

The former ally says he told the governor about the closures while they were happening, but the governor says he doesn't recall the conversation.

It is one of many unresolved questions after the release of a report by attorneys for Mr. Christie's office, which the administration says absolves the Republican governor of any role in the scandal.

David Wildstein, at the time one of Mr. Christie's top lieutenants at the Port Authority of New York and New Jersey, made the allegation over a dinner with Mr. Christie's spokesman on the night before Mr. Wildstein resigned amid the growing bridge scandal, according to the report, which draws on dozens of interviews with members of the administration.

The report, released Thursday, says there is no evidence Mr. Christie knew of the lane closures before they occurred and says it can't establish a firm motive for the closures, which appeared to have been engineered by Mr. Wildstein and another top aide to target the mayor of the borough of Fort Lee, N.J. The resulting traffic jam tied up Fort Lee for a week before the closures were reversed by an official from the New York side of the authority.