The family of Stephen Ivens, 35, reported him missing on Friday morning. They said they last saw him at his residence Thursday evening. A handgun was reportedly missing from his home.
"Special Agent Ivens is known to have been distraught, and investigators believe he my possibly be suicidal," said FBI Special Agent Steve Gomez at a press conference Saturday.
Police believe Ivens, described as an avid hiker and runner, took off on-foot from his home early Friday and may be carrying the gun with him.
Investigators said foul play was not suspected and they do not believe Ivens poses a threat to others.
About 100 FBI agents, 40 sheriff's department rescuers and a dozen local police officers were participating in the search for Ivens.
Gomez said dogs had tracked Ivens' scent toward the rugged Verdugo Mountains, but searchers spread out throughout Los Angeles County.
"For us, this is not necessarily an extraordinary deployment," said Capt. Mike Parker of the Los Angeles County Sheriff's Department. "Considering the circumstances, it would be very similar if it was a private citizen in a similar environment or a similar situation."
Ivens has been an FBI agent for three years, working for national security. He is also a married father of a 1-year-old baby.
Ivens is described as a white male, 6-feet tall and 160 pounds with brown eyes and receding brown hair. He also wears prescription glasses.
Anyone with information on Ivens' whereabouts is asked to contact the Burbank Police Department at (818) 238-3000.