(AP) -- Federal authorities have closed an investigation into whether Gov. Chris Christie's administration threatened to withhold Superstorm Sandy relief money from Hoboken for political reasons.

The information was disclosed in a letter from the U.S. Attorney's Office to lawyers for Marc Ferzan, Christie's former top aide in charge of Sandy recovery.

It was dated Friday, the same day a former Christie ally pleaded guilty and two others were indicted on charges that they schemed to close approach lanes to the George Washington Bridge for political retribution.

At the same time the bridge case was getting heavy publicity more than a year ago, Hoboken Mayor Dawn Zimmer said officials in Christie's administration told her aid to her city could be at risk if she did not support a private real estate development deal the administration favored.

At the time, the law firm of David Samson was representing the developer. Samson was also the chairman of the Port Authority of New York and New Jersey, the powerful bistate transportation agency at the center of the bridge scandal.

Christie and his aides have denied using political pressure on behalf of a developer.

"We are pleased that after a thorough investigation, the Department of Justice has confirmed to me that they have concluded that the claims made by the Mayor of Hoboken had no basis in law or fact," Ferzan's lawyer, George Stamboulidis, said in a statement Friday.

Zimmer said she stands behind her account but accepts the judgment of the U.S. Attorney's Office.