Senator Dianne Feinstein got a serious bomb threat a month before pipe bombs started showing up at the homes and offices of other prominent politicians ... TMZ has learned.
According to court docs ... an intern at the California Senator's field office on Santa Monica Blvd. answered the phone on September 26 and a man on the line wanted to confirm the address of the office. He got mad and blurted out he was gonna "bomb the place" and hung up.
The intern, concerned with what he had just heard, told his supervisor who then contacted Capitol police. According to the docs, cops executed a search warrant for phone records in hopes of identifying the caller.
Law enforcement sources tell TMZ ... no arrests have been made and it's an ongoing investigation.