FWIW, tonight I happened to watch a news report from Sunday night I inadvertently taped following "X-Files." It said the FBI had sent letters to apartment managers throughout Los Angeles (they were reporting from Studio City, next to Encino).
The FBI alert (which was shown on the news report) said "to be on the look-out for suspicious people who might rent an apartment in order to place explosives in the building."
I think they sent out info to all apartments across the country. We received info here in the Cincinnati area also. What I received was very general and in no way helpful. It says, in part, to have on site staff be alert for things out of the ordinary. Specifically items such as gunpower, PVC or metal piping, nails, dismantled kitchen timers and gave a list of phone numbers for the FBI.
Unless the information they received in LA from the FBI was more specific, it seemed mostly just general information.