Nearly 20 new subpoenas have been issued in the probe of lane closures on the George Washington Bridge, and a New Jersey legislative panel insisted that previously subpoenaed documents be turned over.

After a two-hour, closed-door meeting Monday, the New Jersey Legislature's Joint Committee on Investigation said the subpoenas issued to Gov. Chris Christie's former deputy chief of staff Bridget Kelley and former campaign manager Bill Stepien are necessary and relevant to their investigation of the George Washington Bridge scandal.

The committee rejected the argument Kelley and Stepien made on constitutional grounds that they are not required to turn over the documents.

“In fact, the subject of inquiry was valid and was relevant to the committee’s investigation here. That was the first motion," said Assemblyman John Wisniewski, committee chairman. "The second motion considered the objections they had made on constitutional ground — the committee rejected those.”

If they documents are not turned over, the panel authorized its special counsel to take all appropriate legal steps to enforce the subpoena.

The committee also authorized issuing 18 new subpoenas seeking new informationin, but Wisniewski would not identify who will get them or exactly what issues they concern.

The committee is trying to determine who authorized the lane closures that resulted in four days of gridlock surrounding the world's busiest bridge — and why it was done.

Christie has denied any involvement.