As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT GROUNDED - SMOKE ODOR IN CABIN PASSING 12000 FEET; IT WAS A BURNING ELECTRICAL / BURNED POPCORN SMELL. ODOR PREVALENT IN ROWS 10-14 WITH A SLIGHT HAZE PRESENT. ACCOMPLISHED MCM 05-96-70 TO TROUBLESHOOT ODOR. FOUND FAULTY BALLAST FOR CEILING LIGHT AT ROW 18. REMOVED AND REPLACED LIGHT ASSEMBLY PER AMM 33-22-00, NO FURTHER ODORS NOTED.