The train's untimely passing occurred at 11 this morning, and the tracks remain blocked as of this writing (3:20 p.m.). Muni is running shuttle buses to get SoMa passengers to and from the Embarcadero station.

Muni spokesperson Janis Yuen (who the heck is this Janis Yuen? What happened to usual spokespeople Maggie Lynch and Alan Siegel? Did they just give up and go home?) says that the cause of the problem is yet to be determined, but we're thinking that it was that little guy from "Nightmare at 20,000 Feet". Where's Shatner when you need him?