Authorities on Sunday were continuing to search for a 42-year-old San Francisco man wanted on suspicion of possessing explosive materials at his Russian Hill home.
The FBI executed a search warrant at the apartment of Ryan Kelly Chamberlain II at Jackson and Polk streets on Saturday, FBI spokesman Peter Lee said at a news conference Sunday afternoon outside the San Francisco federal courthouse. A nationwide alert was issued to law enforcement in the search for Chamberlain.
Chamberlain was last seen south of San Francisco and is believed to be driving a white 2008 Nissan Altima with either California or Texas license plates 7FQY085 and BX9M042, respectively, according to Lee.
Chamberlain is described as a white man, 6-foot-3 and 225 pounds with brown hair and blue eyes. He is considered armed and dangerous, but it's unconfirmed whether he might have explosives with him, according to the FBI.
The scene that unfolded Saturday involving a search of Chamberlain's residence by hazardous-materials crews left residents of the normally quiet neighborhood feeling uneasy.
"It was very bizarre," said Frank Gallo, who lives nearby at Pacific Avenue and Larkin Street. "They had all these tents. It was very strange for the neighborhood."
At the scene on Saturday, FBI spokeswoman Alice Heller said there was no danger to public safety, which Lee echoed on Sunday. Authorities have not disclosed the cause for the search. The warrant and affidavit remain under seal.
While Lee didn't disclose the type or amount of explosives allegedly found at Chamberlain's apartment, he confirmed, "There is no chemical, biological or radiation known at this time." Additionally, he dispelled news reports that authorities had found ricin, a deadly toxin.
"We do not believe we can conclusively say that there were any sources of ricin at the residence," Lee said.
Chamberlain's motive for allegedly possessing explosives remains unknown. He appears to be active on social media, though Lee didn't confirm whether those outlets are contributing to the investigation.
The investigation is ongoing, and authorities are not seeking any additional suspects in connection with the case.
Randy Bramblett, a personal trainer and professional athlete in San Francisco, said he became friends with Chamberlain through Project Sport, a local sports marketing company. The company let Chamberlain go when it was sold in November and he soon lost touch with friends and stopped returning calls and messages, Bramblett said.
Chamberlain had worked for years as a political consultant on Democratic campaigns, Bramblett said. On a website that appears to be run by Chamberlain, he lists a number of feats under the section "Fun Facts," including that he once turned Lombard Street into a life-size Candyland game and that he was on the team representing former US Airways Capt. Chesley Sullenberger after the legendary Hudson River emergency landing in 2009.
Anyone who sees Chamberlain or has information on his whereabouts is urged to contact the FBI at (415) 553-7400 or dial 911. All calls are confidential. Tips can also be submitted at tips.fbi.gov.
The Associated Press contributed to this report.