2008 Toyota Prius electrical system problems

Toyota prius (2008) - fire after minor accident (battery fire) after a fairly standard rear end collision (25-30 MPH), my toyota prius caught fire and burst into flames. I was stopped at a red light on a city street in chicago, il when the accident occurred, my vehicle was not in motion. Within minutes of impact (to right rear of car), the responding police officer saw fire under the car (began in rear) and the fire dept was called.

All lights suddenly went black, front, back everything. I was going 50 MPH on a mountain road and was on a straight road section out of the curves when everything went black. It was night-time at about 9:30 pm so very dark. I went into shock immediately slammed on brakes, just glad no one in back of me and carefully tried to feel to the side of the road. This is a road with alot of 18 wheelers as it is a major route. Also very curvy, and I was lucky not to get killed!!!!!