What was found
(CAN) AFTER THE PASSENGERS HAD BOARDED THE ACFT, DURING THE STARTING OR SLIGHTLY AFTER THE STARTING OF THE APU, A STATION ATTENDANT NOTICED SMOKE/FLAME COMING FROM THE AREA OF THE APU. THE SMOKE/FLAME WAS REPORTED TO THE CAPTAIN BY A STATION ATTENDANT AND THEN THE CAPTAIN ORDERED A RAPID DEPLANEMENT OF THE ACFT. THERE WERE NO REPORTED INJURIES AS A RESULT OF THE DEPLANEMENT. THE ACFT IS CURRENTLY BEING INSPECTED. APU FAILS TO ACCELERATE MORE THAN 5 PERCENT APU FAIL MESSAGE. GROUND CREW REPORTED VISIBLE FLAME OUTSIDE. NO FIRE WARNING ON EICAS. APU STARTER/GENERATOR REPLACED IAW AMM 49-42-03, PB 401.