The announcements about lawmakers' continued investigation came the day before Christie is to deliver his annual State of the State address.
"There are still more questions than answers, and we cannot rest until we know exactly what happened in Fort Lee," Senate President Stephen Sweeney (D., Gloucester) said in a statement, noting that Sen. Loretta Weinberg (D., Bergen) was the first lawmaker to challenge the Port Authority of New York and New Jersey over the lane closures that caused the jams.
"We plan to work collaboratively with our Assembly colleagues and the committee they have created to get to the bottom of this as soon as possible," Sweeney said.
Weinberg said Monday that she would prefer that lawmakers create a joint committee.
But "in one way, two committees might be better," Weinberg said. If there were gaps in a witness' testimony before one committee, the other could try to address them, she said.
"I think there's enough to keep everybody busy," Weinberg said.
At a news conference, Wisniewski said Weinberg, though not a member of his committee, had been "an invaluable partner" whom he envisioned "continuing to have a role working with me as we move forward."
Prieto said he wanted to ensure continuity in the investigation. With the work Wisniewski's committee has done, Prieto said, "we can just expand from there, with all the proper tools this committee will now have at its disposal to keep moving forward."
Last week, documents subpoenaed by Wisniewski's committee revealed that a top aide in Christie's office had sent an e-mail to a Port Authority official in August, saying it was "time for some traffic problems in Fort Lee."
A day that and other e-mails were disclosed, Christie fired the aide, Bridget Anne Kelly.
The Republican governor - who maintains he had known nothing of the alleged plan to snarl traffic - also dismissed a close political adviser, Bill Stepien, who was implicated in the e-mails.
On Friday, Democrats released more than 2,000 pages of documents obtained from subpoenas of seven Port Authority officials, including David Wildstein and Bill Baroni. Both resigned in December after Baroni, a Christie appointee, testified that the closures were conducted as part of a traffic study overseen by Wildstein.
The documents reveal that several of Christie's senior staff members had received notice of the traffic jams as early as September, while the closures were underway. One senior aide was forwarded an e-mail from the Port Authority's executive director, Patrick Foye, an appointee of New York Gov. Andrew Cuomo, who blasted the closures as "abusive" and said the decision possibly violated state and federal laws.
On Monday, Fort Lee Mayor Mark Sokolich, a Democrat who did not endorse Christie's reelection, said he had been asked to endorse the governor, the Associated Press reported. Sokolich previously said he did not remember being asked for an endorsement and did not know why he would be targeted.
Wisniewski said Monday that it would be "premature" to say which Christie staffers the committee might subpoena, and whether that list would include the governor.
The investigation will proceed on "a piece-by-piece basis," likely starting with Kelly and extending to others who may have been involved in the decision, Wisniewski said.
"In the context of a governor running for reelection, it strains credibility to say that all of these senior people whose job it is to communicate and keep the governor informed did absolutely nothing with these e-mails," Wisniewski said.
On Monday, Wisniewski referred contempt charges against Wildstein to the Mercer County Prosecutor's Office. Appearing before Wisniewski's committee last week, Wildstein repeatedly refused to answer questions. His lawyer, Alan Zegas, suggested he was looking for immunity from prosecution.
Wisniewski said Monday that was a matter for Zegas and Wildstein to address with law enforcement.
The number of members on the Assembly committee and the partisan balance have not been decided, Prieto said. And the outside counsel - whom Wisniewski said would provide needed resources - also has not been selected. A decision could be announced by Wednesday, he said.
"We have not set the parameters yet of what this committee is going to do," Prieto said. "Anything that's an abuse of power, we want to know about."
The Assembly and Senate both plan to call special sessions Thursday to authorize the investigatory committees and the use of subpoena power.
Wisniewski, whose subpoena power expires at noon Tuesday, said he would wait until the authority was renewed to issue more subpoenas.
A Monmouth University/Asbury Park Press poll released Monday found Christie's job approval rating had taken "a slight hit" since one month ago, falling from 65 percent to 59 percent - the first time the rating had dropped below 60 percent since Hurricane Sandy.
The poll, conducted from Friday to Sunday, found that 83 percent of New Jerseyans are paying attention to the George Washington Bridge story. A majority - 52 percent - believe Christie was not involved, though 80 percent expect that more staffers will be implicated, according to the poll.
Nationally, the story has drawn far less attention, according to a Pew Research Center survey, which found that 18 percent of adults surveyed between Thursday and Sunday paid very close attention to Christie's apology.