FBI agents searched the home of a Los Angeles deputy mayor this week as part of an investigation into whether he made a bomb threat against city hall, officials said.

A statement from the office of the LA mayor, Karen Bass, said she was notified of Tuesday’s search at the residence of Brian K Williams, her deputy mayor for public safety, as part of an investigation into an alleged threat.

The Los Angeles police department confirmed that officers responded “earlier this year” to a bomb threat against city hall.

“Our initial investigation revealed that the source of the threat was likely from Brian Williams, deputy mayor for public safety,” the department said in a statement on Wednesday. “Due to the department’s working relationship with Mr Williams, the investigation was referred to the FBI. The FBI remains the investigating agency.”

Williams’ attorney, Dmitry Gorin, told the Los Angeles Times that his client “strongly maintains his innocence and intends to vigorously fight the allegations”.

Zach Seidl, a spokesperson for Bass, said Williams has been placed on administrative leave.

“The mayor takes this matter very seriously,” Seidl said in a statement. “When the threat was reported, LAPD investigated and determined there was no immediate danger. Following additional investigation, LAPD referred this matter to the FBI for further investigation.”

Williams has not been arrested or charged and Gorin said his client was cooperating with investigators.

“He has a lengthy career of public service and is presumed innocent of these allegations,” Gorin said.

Williams has spent nearly two years as a deputy mayor in Bass’s office, working on issues such as police hiring, public safety spending and the search for a new police chief.

He was also a deputy mayor from 2001 to 2005 during the administration of then mayor James K Hahn. Before that, Williams spent several years as an assistant city attorney in Los Angeles, the Times said.