According to SFist Jonathan, "My train is stopped in Burlingame @ 6:20 pm -- the conductor says the train is being held here due to a bomb threat at Millbrae."

Word is the threat shutdown BART and CalTrain in the area, indefinitely.

We'll update as soon as we know more.

Update 7:41: Jonathan tells us, "[The threat] it's still on. All caltrains stopped 'indefinitely' and no BART service to Millbrae. About 15 cyclists abandoned the train in Burlingame after the conductor announced that the delay might be 3 hours ... [N]ow at the San Bruno BART station [where] BART is running."

Upate 8:30: Suspicious package "deemed harmless." Trains start running and BART station reopens.