(CNN) - A special New Jersey state legislative committee investigating the George Washington Bridge scandal that has upended Gov. Chris Christie’s administration has issued its first subpoenas for oral testimony.
The panel said it had served Pat Foye, the executive director of the Port Authority of New York and New Jersey, agency board member William Schuber, Christie spokesman Michael Drewniak and Christina Renna, who worked under Christie’s former deputy chief of staff Bridget Anne Kelly, a key figure in the scandal.
Renna and Schuber were asked to testify on May 6, and the other two on May 13.
“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 committee’s Democratic co-chairs, Senate Majority Leader Loretta Weinberg and Assemblyman John Wisniewski, said in a statement.
The panel already has issued a number of subpoenas for documents and other information related to the investigation of suggestions top Christie appointees orchestrated traffic jams around the nation’s busiest bridge in Fort Lee last year as part of an alleged political payback scheme.
Wisniewski said investigators still only have a partial picture of what happened in the period before access lanes to the bridge were deliberately closed over a four-day period last September.
The most sensational piece of evidence unearthed so far is an email from Kelly to David Wildstein, a Port Authority executive that read:
“Time for some traffic problems in Fort Lee.”
Wildstein replied: “Got it.”
Wisniewski told CNN that investigators “still don’t know what happened before that email,” which was sent weeks before the lane closures occurred.
“The testimony will help us get to that point where we'll ultimately be able to answer those questions,” Wisniewksi said.
The four Republican members of the committee believe they already have enough information to craft legislation aimed at preventing abuse of authority.
“We don’t understand the reason for waiting,” Assemblywoman Amy Handlin said. “It’s fine to continue to hunt for clues as to why Bridget Kelly and the others did what they did but we can walk and chew gum at the same time.”
Kelly went to court and successfully fought off her subpoena from the committee for documents and other information. She was not asked to testify.
Christie has repeatedly denied having had any role in the planning of the lane closures or having known about them ahead of time.
An internal review conducted by lawyers hired by Christie’s office cleared him of any wrongdoing and pointed the finger at Kelly and Wildstein. Critics claim that review was a whitewash.
On Monday, Christie would not discuss whether he expected to be called to testify before the legislative committee.
The U.S. Attorney’s office is also investigating the matter, and a grand jury has heard from witnesses.