The New Jersey legislative panel investigating September lane closures at the George Washington Bridge has called four people - current and former members of the Christie administration and officials at the Port Authority of New York and New Jersey - to testify next month.

The recipients of subpoenas that were announced Tuesday are Gov. Christie's press secretary, Michael Drewniak; former administration official Christina Genovese Renna; Patrick Foye, executive director of the Port Authority; and William "Pat" Schuber, a Christie-appointed commissioner at the authority.

These are the first subpoenas issued by the joint committee to compel oral testimony about the traffic jams, allegedly carried out for political retribution against the Democratic mayor of Fort Lee, Bergen County.

Since January, the panel has received thousands of pages of documents in response to about 30 subpoenas seeking the production of documents about the lane closures. The committee recently suffered a setback when a Superior Court judge ruled that two former top aides to Christie did not have to produce documents.

The U.S. Attorney's Office in Newark also is investigating the lane closures.

Each of the four called to testify, either May 6 or 13, had received document subpoenas. An attorney for Renna said she would testify, and a spokesman for Foye said he would as well. Schuber could not be reached, and Drewniak's attorney did not respond to a message.

Drewniak testified as a witness this month before a grand jury as part of the U.S. attorney's investigation.

"With these subpoenas for testimony, the joint committee is moving to a key stage of its investigation into how this abuse of government power and threat to public safety occurred," the panel's cochairs, Assemblyman John S. Wisniewski (D., Middlesex) and Senate Majority Leader Loretta Weinberg (D., Bergen), said in a statement Tuesday.

"The four people we've called to testify can begin providing insight into the troubling environment that allowed something as concerning as these lane closings to happen," they said.

Christie has said he had no knowledge of the lane closures, and a law firm retained by his office issued a report that it said cleared the governor and his current staff of any responsibility. Critics have slammed the report, released last month by Gibson, Dunn & Crutcher L.L.P., as a whitewash.

The report said David Wildstein, a former Christie appointee at the Port Authority, and Bridget Anne Kelly, the governor's former deputy chief of staff, orchestrated the lane closures. E-mails released by the panel show Kelly called in August for "some traffic problems in Fort Lee," to which Wildstein replied, "Got it."

Christie fired Kelly when the e-mail exchange surfaced in January.

Called in January to testify before an Assembly committee, Wildstein invoked his Fifth Amendment right against self-incrimination and declined to answer questions.

In December - as the bridge scandal started causing a political headache for the Republican governor - Christie's chief of staff asked senior aides if they had knowledge of the lane closures.

Thereafter, Kelly asked Renna, who worked in her office, to delete a potentially incriminating e-mail about Fort Lee Mayor Mark Sokolich, according to the Gibson Dunn report. Renna preserved the e-mail.

She resigned in January.

Drewniak told Gibson Dunn that Wildstein, his friend, said he told Christie about the lane closures at a Sept. 11 event while they were still happening. Christie has said he does not recall such a conversation.

Foye, an appointee of New York Gov. Andrew Cuomo, told the Assembly Transportation Committee in December that Wildstein was responsible for the lane closures. Foye also disputed a claim by Christie appointee Bill Baroni that the closures were part of a traffic study.