As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT RETURNED TO GATE IN DEN WITH SMOKE IN CABIN FROM A OVERHEATED PACK. NR 3 BUS TIE TRIPPED (UNDEREXCITATION), ATTEMPTED RESET SUCCESSFUL. LT PACK OVERHEAT WITH GOOD INDICATION OF POWER DRAW WHEN PACK TURNED ON. *S/D* RESET LEFT PACK SWITCH, RAN ENGINES AND CYCLED PACK SWITCHES AND ALL INDICATIONS NORMAL.