The FBI and local law enforcement agencies called a news conference Monday to discuss what the FBI calls a "non-corroborated" threat involving the Los Angeles area.
The FBI did not elaborate on the nature of the threat except to say authorities haven't determined yet whether it is credible.
The Los Angeles Times reports that the Sheriff's Department is stepping up security at transit stations across the area after a threat to blow up the commuter rail station in Universal City.
The station is adjacent to Universal CityWalk, an area filled with restaurants, nightclubs and other entertainment activities and often crowded.
Sheriff's Department Chief Scott Edson tells the Times authorities have decided to step up security at Universal City and other stations based on recent information.