As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) AFTER FLIGHT 5401 FROM CVG TO TOL, WHILE PARKED AT THE GATE WITH APU RUNNING GOT A SMOKE TOILET WARNING MSG & LAV SMOKE DETECTOR WAS BEEPING. ALSO SMOKE IN THE CABIN. PERFORMED QRH, SMOKE DETECTOR STOPPED BEEPING & WARNING MSG CLEARED, AND CALLED FOR FIRE TRUCK. NO PAX WERE ON BOARD.FOUND DUCT P/N 14243-101 FROM RT PRSOV TO RT PACK HEAT EXCHANGER CRACKED.