BERMAN: Los Angeles authorities are asking residents to remain calm but vigilant about a threat against the city subway station. The FBI says a warning about a potential bombing of the Universal City Station came in on an international tip line leading officials to increase security across the entire Los Angeles County transit system.</s>BOLDUAN: Joining us now for more on the details is CNN's national correspondent, Kyung Lah. She's been looking into this. Kyung, what are you picking up?</s>KYUNG LAH, CNN NATIONAL CORRESPONDENT: Good morning, John and Kate. We're getting a little more information from the mayor of Los Angeles. He says that this anonymous tip, which was phoned in from overseas, that the caller was actually reporting something that that caller had heard from somebody else. Well, that information was then handed over to L.A. authorities and they decided to respond by holding this press conference last night. So why make this information public? Well, the mayor says that they get these kinds of tips all the time, but what's concerning to them is that it was very specific --
Warning About Plot To Blow Up L.A. Subway System.