As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) FLIGHT CREW REPORTED SMOKE IN CABIN ON TAKEOFF. ACFT RETURNED TO BLOCKS. MX CALLED AND MEL`S ACFT. MIXING VALVE FOUND TO HAVE A CRACKED AND DAMAGED BUTTERFLY VALVE. MIXING VALVE REPLACED AND GROUND RUNS CARRIED OUT AND SHOWED NO SIGNS OF SMOKE.