What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Narrative: during take-off and after landing gear retraction, the main bleed air valves were opened to pressure the aircraft, but immediately following their opening smoke filled the cabin and cockpit areas. The main air valves were then closed and emergency procedures were accomplished during which a request for return and landing was made to the tower. Landing and taxi to the ramp was made without further incident and the passengers and crew departed the aircraft. Preliminary and detailed investigation indicated that hydraulic fluid had entered the environmental system through a failed check valve.
As the FAA filed it
NARRATIVE: DURING TAKE-OFF AND AFTER LANDING GEAR RETRACTION, THE MAIN BLEED AIR VALVES WERE OPENED TO PRESSURE THE AIRCRAFT, BUT IMMEDIATELY FOLLOWING THEIR OPENING SMOKE FILLED THE CABIN AND COCKPIT AREAS. THE MAIN AIR VALVES WERE THEN CLOSED AND EMERGENCY PROCEDURES WERE ACCOMPLISHED DURING WHICH A REQUEST FOR RETURN AND LANDING WAS MADE TO THE TOWER. LANDING AND TAXI TO THE RAMP WAS MADE WITHOUT FURTHER INCIDENT AND THE PASSENGERS AND CREW DEPARTED THE AIRCRAFT. PRELIMINARY AND DETAILED INVESTIGATION INDICATED THAT HYDRAULIC FLUID HAD ENTERED THE ENVIRONMENTAL SYSTEM THROUGH A FAILED CHECK VALVE.