Top aides to New Jersey's Republican governor are among 20 people and organisations subpoenaed over a bridge traffic jam scandal that has shaken the state administration.
Chris Christie's chief of staff, chief counsel and top communications aide were among those to receive subpoenas on Thursday and yesterday. The Christie for Governor campaign organisation also was subpoenaed, although the governor himself was not.
The subpoenas seek documents in connection with a plot, which may have been carried out to settle a political score, to deliberately close traffic lanes near the George Washington Bridge, one of the world's busiest crossings, causing four days of gridlock.
It gives Mr Christie a chance to convince long-time financial supporters and wealthy newcomers that the scandal has not hurt his national stature and potential as a US presidential candidate in 2016.
A lawyer representing one person implicated in the plot said his client would give evidence if granted immunity from prosecution.
Mr Christie has apologised for the traffic jams, saying they "blindsided" him and has called his staff's behaviour "stupid".
The subpoenas seek documents that could shed light on who was behind the plot to create the traffic jams in Fort Lee and whether it was done to settle a political score.
Some people who are being asked to turn over text messages and emails could be called to give evidence later. Documents must be returned early next month.
Democratic Assemblyman John Wisniewski, who is heading the legislative investigation, said Mr Christie was not a target.
"What we're really looking at is the why," he said. "We know who sent out the request to close those lanes. We know who received it. We don't know why it was sent. We don't know who gave that person authorisation to send it. We don't know why she felt empowered to send it."
The scandal broke wide open last week with the release of documents showing that a top Christie aide sent a message saying "time for some traffic problems in Fort Lee" to David Wildstein, the governor's No 2 at the agency that runs the George Washington Bridge. Mr Wildstein, replied: "Got it."
About three weeks later, Mr Wildstein watched as two of three approach lanes to the bridge were blocked off in Fort Lee, backing up local traffic into town for four days. It appears the plot may have been carried out to settle a political score, possibly against Fort Lee's mayor, a Democrat who declined to endorse Mr Christie.
The investigation into the lane closings threatens to upend Mr Christie's second term and derail any presidential ambitions. Four members of his circle, including Mr Wildstein, a friend since high school, have lost their jobs.
Mr Wildstein's lawyer Alan Zegas said yesterday that his client was ready to give evidence if granted immunity from prosecution by the US attorney's office, which is reviewing the matter. Mr Wildstein refused to answer questions when called before the legislative panel, invoking his right against self-incrimination.
"If he has immunity from the relevant entities, he'll talk," Mr Zegas said.
Mr Wildstein, whom Mr Christie appointed to a position in the Port Authority of New York and New Jersey, supplied a legislative committee with the most damning documents in the case, including the email from sacked deputy chief of staff Bridget Kelly giving the go-ahead for the lane closings in mid-August.
Mr Christie has denied any knowledge of the plot.
On Thursday, his administration announced it had hired a legal team to deal with investigations by state politicians, a US senator and federal prosecutors. The legislative committee also hired an outside counsel, Reid Schar, who helped convict former Illinois governor Rod Blagojevich of corruption.