(CNN) -- The FBI has questioned people connected to Chris Christie's former campaign manager as part of a federal probe of a traffic scandal that has upended the New Jersey governor's administration, court papers show.
Bill Stepien, in arguing why he cannot comply with a subpoena issued by a state legislative committee also investigating the scandal, said federal agents have visited his home and questioned people who know him, according to court papers.
"In recent weeks, federal criminal investigators have made their interest in him plain, traveling to his home and importuning his landlord and presumably others to provide information about his conduct and character," Stepien's lawyer, Kevin Marino, said.
Specifically, the court documents claimed that an agent called Stepien on his cell phone in January and most recently questioned his landlord.
The FBI asked "if he was married, was a rowdy tenant, did he pay his rent on time," according to the papers.
The FBI has been investigating Bridget Anne Kelly as well, said her attorney, Michael Critchley. Kelly is another Christie appointee fighting a legislative subpoena.
Agents visited her house and spoke with her parents; they also visited her father's job last month, Critchley said.
The U.S. attorney's office in New Jersey contacted Critchley to see whether Kelly would be interested in talking, and he told them she was not, he said.
These visits are the first indications that investigators have been looking to question those with close ties to Christie.
Stepien managed both Christie gubernatorial campaigns, but Christie asked him to leave his political organization in January after his name surfaced in e-mails around the scandal involving abrupt traffic lane closures near the George Washington Bridge in Fort Lee last September.
Kelly was Christie's deputy chief of staff for legislative and intergovernmental affairs, and her name surfaced in those e-mails as well. Christie fired her after the e-mails became public.
Both federal and legislative investigators are probing suggestions that top Christie appointees orchestrated the lane closures as part of a political scheme to punish the mayor of Fort Lee for not endorsing Christie for re-election.
Stepien has not been accused of any wrongdoing, and Christie denies knowing about the traffic gridlock until after it happened.
Christie, a Republican viewed as a possible presidential candidate in 2016, also has said repeatedly he knew nothing about any related political mischief by people working on behalf of the state.
Critchley said he plans to file court papers on Thursday.
The U.S. attorney's office in Newark had no comment on the Stepien matter.