TRENTON, N.J. — Federal prosecutors have escalated their criminal investigation into allegations that Gov. Chris Christie’s aides created traffic jams as political payback, subpoenaing his re-election campaign and the state Republican leadership.

The subpoenas seek documents related to the closure of traffic lanes near the George Washington Bridge, said attorney Mark Sheridan, who represents the Christie for Governor organization and the Republican State Committee.

Additional Photos In this Jan. 14, 2014 file photo, New Jersey Gov. Chris Christie delivers his State Of The State address at the Statehouse in Trenton, N.J. Christie’s re-election campaign and the state Republican party have less than two weeks to comply with subpoenas from federal prosecutors investigating allegations of political payback. Subpoenas to the Christie for Governor organization and the Republican State Committee were disclosed Thursday, Jan. 23, 2014, the same day the Republican governor’s campaign announced it had hired a Washington, D.C., law firm in the case. AP Photo/Julio Cortez

The subpoenas were disclosed Thursday, the day the Republican governor’s campaign announced it had hired the Washington, D.C., law firm Patton Boggs in the case. Sheridan works for the firm and is general counsel for the state Republican committee.

A state legislative committee investigating the traffic jams also has issued a subpoena to the Christie campaign.

“The campaign and the state party intend to cooperate with the U.S. attorney’s office and the state legislative committee and will respond to the subpoenas accordingly,” Sheridan said.

The joint legislative probe is continuing, Sen. Loretta Weinberg said. Weinberg, a Democrat, said the lawmakers have not been asked to suspend their investigation. Documents from an original batch of subpoenas by the Assembly transportation committee caught the attention of federal authorities.

The federal subpoenas are due Feb. 5. The state committee subpoenas must be returned Feb. 3.

Earlier this month, U.S. Attorney Paul Fishman said only that his office was reviewing the matter “to determine whether a federal law was implicated.”

Christie, a potential presidential candidate in 2016, was New Jersey’s U.S. attorney before stepping down in late 2008 to run for governor.

Federal prosecutors refused to comment Thursday. Christie, in Camden to talk about a school dinner program, left without taking any questions.

The traffic lanes were closed for four days in September, creating traffic gridlock in Fort Lee, the town at the base of the bridge, which connects New Jersey and New York City. Some of Christie’s aides initially said the closures were part of a traffic study, but emails and text messages turned over to legislators suggest it may have been a message to the town’s Democratic mayor for not endorsing Christie.

Four people close to Christie have been fired or resigned as the scandal has unfolded, including Christie’s two-time campaign manager, Bill Stepien.

Emails subpoenaed in the state investigation and released publicly this month showed Stepien appearing to gloat over the traffic chaos the lane closures caused. Emergency vehicles, school buses and commuters were delayed, some for hours.

After learning of the correspondence, Christie asked Stepien to withdraw a bid to become the next state GOP chairman, saying he was disturbed by Stepien’s “callous indifference.” Stepien had widely been seen as a potential campaign manager in a Christie presidential run.

The emails, mostly sent from private accounts, also showed the involvement of Christie’s deputy chief of staff, Bridget Kelly, whom he fired.

“Time for some traffic problems in Fort Lee,” Kelly emailed to a Christie loyalist at the agency that runs the bridge about three weeks before the lanes were abruptly blocked to local traffic.

“Got it,” replied the recipient, David Wildstein, Christie’s No. 2 man at the agency.

Wildstein and Christie’s top deputy at the agency, Bill Baroni, have resigned.

Legal experts have said possible charges arising out of the political payback scandal could range from conspiracy and official misconduct to perjury or obstruction. They said the easiest charge to bring might be conspiracy, given that documents have already shown a number of people working together to shut down a road for apparently illegal purposes.

If it turns out the purported traffic study was produced in an attempt to conceal political retribution, the experts said, obstruction charges could be brought.

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