ABC News Exclusive: Grand Jury Convened in Christie Bridge Scandal Probe A grand jury has been convened to look further into the matter.

 -- The U.S. Attorney in New Jersey has convened a grand jury to investigate the involvement of Governor Chris Christie’s office in the George Washington Bridge scandal, ABC News has learned.

Twenty-three jurors convened in a federal courthouse in Newark today to hear testimony from a key staff member, Christie press secretary Mike Drewniak, whose lawyer, Anthony Iacullo, said Drewniak was not a target of the investigation.

"We're here to answer questions and that's what Michael did today," Iacullo said.

The convening of the grand jury is evidence that the U.S. Attorney’s investigation has progressed beyond an inquiry and moved to the criminal phase.

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The grand jury, which will meet for up to the next 18 months, has the power to indict, subpoena and interview witnesses without their attorney's present.

This marks for the first time confirmation that what started out as a preliminary inquiry into the governor’s office has now become a criminal investigation into the activities that led to gridlock traffic across the bridge from Manhattan in Fort Lee.

Drewniak was inside the courthouse for more than two hours.

Iacullo, who spoke exclusively with ABC News, said, "I'm not going to get into the specifics as to what would be discussed in the grand jury. I would say though that Mike is a witness and we have been assured that he continues to be a witness throughout these proceedings and Mike has continued to cooperate as requested by the government into this inquiry."

He declined to comment about anything regarding whether Christie had personal knowledge or direct role in the shutdown of the lanes.

ABC News has also learned from two officials briefed on the investigation that a team of state prosecutors -- tapped by Christie's own attorney general -- are monitoring the federal case and are prepared to continue the investigation on the state level if the feds turn it over to them.

Paul Loriquet, a spokesman for acting N.J. Attorney General John Hoffman, declined to comment.

The grand jury is composed of residents from northern New Jersey who will come in every Friday or every other Friday. Grand juries typically last about 18 months, but can be extended. The grand jurors sit in closed door meeting listening to the prosecutors question witnesses, who must respond under the wide ranging subpoena authority of the grand jury.

The final decision on whether or not to indict or file charges against Governor Christie or anyone in his office comes from the decision of the grand jury.