The airplane was pushed back from the gate and the left engine was started with no discrepancies reported. During the starting of the right engine, numerous passengers saw torching aft of the tailpipe. A commotion ensued which drew the attention of the three of the four flight attendants who reported seeing an orange glow either inside or outside the airplane. The captain later reported there were no abnormal engine indications in the cockpit, but he then secured the right engine. The captain secured the left engine after simultaneously noticing passengers on the ramp and illumination of entry door lights. A flight attendant reported a male passenger (who was bigger than her) approached her at door 2L and attempted to open the door by partially rotating the 2L door handle. The door did not open completely but was ‘cracked.’ The flight attendant eventually opened the door fully and locked it against the fuselage. The male passenger exited immediately, followed by several other passengers. She then opened the 2R door and passengers exited it as well. Passengers also evacuated the airplane via the 3L and 3R doors, which a flight attendant opened. Readout of the flight data recorder revealed that at the time the fuel cutoff switch for the right engine was recorded to be in the “run” position, the recorded fuel flow was 1,696 PPH. Within approximately 2 seconds of the right engine fuel cutoff switch being in the “run” position, the fuel flow was recorded to be 3,136 PPH. The maximum recorded fuel flow of 6,272 PPH occurred 2 seconds before the fuel cutoff switch was recorded to be in the “cutoff” position, or 24 seconds after the fuel cutoff switch was in the “run” position. In contrast, within 4 seconds of the left engine fuel cutoff switch being in the “run” position for engine start, the recorded fuel flow was 544 PPH. Further review of the previous eight engine starts revealed the left and right fuel flows were nearly matched, with no recorded fuel flow value greater than 580 PPH within the first 4 seconds after the fuel cutoff switch was recorded to be in the “run” position. The flight crews are trained that during hot starts, the fuel flow almost immediately exceeds 700PPH. The engine start procedures checklist indicates the engine start is to be aborted if abnormally high or fluctuation fuel flow is noted. Probable Cause: a torching of the right engine caused by an abnormally high flow fuel during engine start for undetermined reasons. The torching resulted in an unwarranted evacuation of the airplane and serious injuries to three passengers . A contributing factor in the accident was the failure of the flightcrew to abort the engine start due to abnormally high fuel flow indication during the right engine start.