According to multiple reports, the FBI questioned aides to Hoboken Mayor Dawn Zimmer, who confirmed that the mayor informed them in May about an alleged threat from New Jersey Lt. Gov. Kim Guadagno to withhold Hurricane Sandy funding. It marks an apparent escalation of both the investigation and the likelihood that the administration of Gov. Chris Christie behaved improperly. His campaign organization, meanwhile, is lawyering up.

Update, 2:30 p.m.: Here's why the lawyers were called in: The New York Times reports that the state Republican party and Christie's reelection campaign have been served with subpoenas from a federal grand jury.

MSNBC's Michael Isikoff reports that Zimmer told the FBI that at least five people could corroborate that she told them about the threat from Guadagno, demanding approval of a real estate project before relief money would be distributed, last spring. That's well before a deputy chief of staff for Christie authorized a controversial closure of access lanes to the George Washington Bridge in September, which prompted new scrutiny on Christie earlier this month. Isikoff:

David Mello, a member of the Hoboken City Council, told NBC News that Zimmer told him about the Guadagno conversation last summer, either in late July or early August as they were walking home after an event. “I distinctly remember [Zimmer] saying that the lieutenant governor said, ‘If this came out, she would deny it,’” he said.

Mello also called the threat "absurd and outrageous." The New York Times reports that two of the four other people interviewed by the FBI were staffers for Zimmer, who became mayor of Hoboken following the arrest of her predecessor. Over the weekend, she spoke with the U.S. Attorney investigating the alleged threat for several hours.

Christie has been content to let the New Jersey legislature's investigation into the bridge scandal unfold. His campaign organization, which has been subpoenaed by that investigation, hired prominent legal counsel according to NJ.com.

The Patton Boggs attorneys representing the campaign are Bob Luskin and Mark Sheridan. Luskin is famous for his defense of numerous high profile figures including Republican operative Karl Rove in the leak of the identity of a CIA officer and bicyclist Lance Armstrong in his blood doping defense.

That's a mixed track record: Rove wasn't charged. Armstrong was eventually banned from the sport for life.