Law enforcement officers in Southern California have launched a massive search in rugged mountain terrain for a missing FBI agent who was said to be despondent and possibly suicidal.

About 100 FBI agents, 40 sheriff's department rescuers and a dozen local police officers participated in the search for Los Angeles-based Special Agent Stephen Ivens, who remained missing late Saturday. He was described as an avid hiker and runner.

FBI Special Agent Steve Gomez said dogs had tracked Ivens' scent toward the rugged Verdugo Mountains, east of Burbank, but searchers were fanning out throughout Los Angeles County.

Ivens, 35, was last seen by family members Thursday evening, KABC-TV reported (http://bit.ly/K6vDfr). He left his Burbank home the next morning on foot and had not been seen since, FBI officials said at a news conference.

Ivens was distraught and authorities fear he may have harmed himself, according to KABC-TV. Officials did not say why Ivens was distraught.

A search of his home did not turn up his handgun and police believe he may have taken it with him.

Ivens was described by FBI colleagues as well liked. Married with a one-year-old child, he has been working for the FBI for the past three years in the national security area. Prior to that, he worked as a Los Angeles police officer for eight years.

Gomez told reporters that foul play was not suspected and Ivens was not believed to pose a threat to others.

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Information from: KABC-TV, http://abclocal.go.com/kabc/