(CNN) -- Ryan Kelly Chamberlain II, a San Francisco man accused of having explosive materials at his home, is in custody, an FBI source said Monday.
Chamberlain was arrested in Crissy Field, a scenic waterfront area where the Golden Gate Bridge spans the Pacific entrance to San Francisco Bay, a U.S. law enforcement official said.
Police have cordoned off the area to search Chamberlain's white Nissan Altima, the official said.
Authorities had been looking for him since the weekend.
Chamberlain, 42, was last seen Saturday south of San Francisco, the FBI said.
"We don't know the intent or motive yet," FBI agent Peter Lee told reporters over the weekend, stressing there was no threat to public safety.
The FBI said then that Chamberlain should be considered armed and dangerous.
Chamberlain's block was closed for some 15 hours over the weekend as investigators searched and cleared the area, CNN affiliate KTVU reported.