What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
When airborne after takeoff pilot saw what he thought was electrical sparks/smoke coming out under panel. Smoke was light and dissipated quickly. Pilot declared emergency and landed. Maintenance discovered some remains of ashes in heat shroud around muffler from a smallpiece of paper or other combustible that had somehow entered the muffler/heat shroud and caused sparks and smoke to enter cabin through heat ducts. Cause unknown at this time.
As the FAA filed it
WHEN AIRBORNE AFTER TAKEOFF PILOT SAW WHAT HE THOUGHT WAS ELECTRICAL SPARKS/SMOKE COMING OUT UNDER PANEL. SMOKE WAS LIGHT AND DISSIPATED QUICKLY. PILOT DECLARED EMERGENCY AND LANDED. MAINTENANCE DISCOVERED SOME REMAINS OF ASHES IN HEAT SHROUD AROUND MUFFLER FROM A SMALLPIECE OF PAPER OR OTHER COMBUSTIBLE THAT HAD SOMEHOW ENTERED THE MUFFLER/HEAT SHROUD AND CAUSED SPARKS AND SMOKE TO ENTER CABIN THROUGH HEAT DUCTS. CAUSE UNKNOWN AT THIS TIME.