The administration of New Jersey Governor Chris Christie has hired a high-powered legal firm to help his office as federal prosecutors investigate whether any laws were broken when a top aide ordered seemingly politically motivated traffic jams.

Christie, a likely 2016 Republican White House contender, turned to a former deputy of ex New York Mayor Rudolph Giuliani, another Republican with presidential aspirations, after revelations that a former aide called for "traffic problems" at the George Washington Bridge in apparent retribution against a local Democratic mayor.

About 20 subpoenas were issued in the case on Thursday, according to Democratic state Assembly member John Wisniewski. They included some 17 people and three organizations, he said, but no names would be disclosed until subpoenas are served.

He said Christie was not among those subpoenaed.

The governor's office said it retained the law firm of Gibson, Dunn & Crutcher LLP to help with an internal review and to cooperate with an investigation announced last week by U.S. Attorney for New Jersey Paul Fishman.

Randy Mastro who in the 1990s served as chief of staff and deputy mayor for operations to Giuliani will lead the team.

The outside attorneys will bring a "third-party perspective to the situation, and they will be a valuable asset as we move forward," Christie spokesman Michael Drewniak said in the statement announcing the law firm's hiring.

Working for the Giuliani administration, Mastro led efforts to clean up Times Square and rid organized crime from the city's Fulton Fish Market, private carting industry and popular San Gennaro Festival.

In private practice since then, he frequently took on the administration of Giuliani's successor, Michael Bloomberg.

Gibson Dunn's partners charge $980 an hour on average, according to a survey published by the National Law Journal.

Christie's statement indicated the administration has retained the law firm, and a spokesman did not return calls regarding whether it would be paid for with taxpayer or personal funds.

CHRISTIE VOWS COOPERATION

The New Jersey governor said last week he would cooperate with the federal probe into the abrupt four-day shutdown in September of two local access lanes to the George Washington Bridge linking New Jersey and New York City.

The move caused massive traffic jams in Fort Lee, angering commuters and delaying school buses and ambulances.

E-mails released last week appeared to link two of Christie's top aides to the decision to snarl traffic in Fort Lee in an effort to punish the town's Democratic mayor for not supporting the governor's re-election effort.

Christie has adamantly denied being part of the apparent scheme and fired his deputy chief of staff, Bridget Anne Kelly, and severed ties with former campaign manager Bill Stepien over their seeming orchestration of the lane closures.

New Jersey lawmakers are also expanding their probe of the scandal, which has become known as "Bridgegate." Both houses of the state legislature scheduled special sessions on Thursday to empanel committees with subpoena power to investigate the closures and any further links to Christie's office.

An investigative panel commissioned by the state assembly said on Thursday it would receive special legal assistance from former Assistant U.S. Attorney Reid Schar, who was lead investigator and prosecutor in both corruption trials of former Illinois Gov. Rod Blagojevich.

Christie is also facing a review by the U.S. Department of Housing and Urban Development over whether his administration may have misused about $2 million in Superstorm Sandy relief funds for an ad campaign that featured him and his family helping with cleanup.

Christie said at a news conference last week that he was "blindsided" by revelations that Kelly, one of his closest advisers, had sent an e-mail in August saying: "Time for some traffic problems in Fort Lee."

The recipient of that e-mail, David Wildstein, a Christie appointee at the Port Authority of New York and New Jersey, which oversees operations at the bridge, responded: "Got it."

Wildstein and his superior, Bill Baroni, also a Christie appointee at the Port Authority, both resigned late last year amid controversy over the closures.