What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Flight departed ord and while climbing out of 700 feet, both pilots "noticed smoke billowing into the cockpit". Crew declared an emergency and requested an immediate return to ord. The smoke/fumes began to dissipate during their approach and flight made a normal landing. After landing the passengers disembarked using the the pax entry door and were taken by bus to terminal.
Because of the cold temperature, one of the flight attendants suffer a little frostbite to a finger while holding an O2 bottle. She was treated on the seen by EMT(s).
Maintenance personnel arrived and noticed a strong odor of deice fluid when running APU bleed system which dissipated after 15-20 minutes of running the packs.
It appears that during the deicing/anti-icing process, fluid was injested into the APU and into the bleed/conditioned air system of the aircraft causing smoke/fumes.
As the FAA filed it
FLIGHT DEPARTED ORD AND WHILE CLIMBING OUT OF 700 FEET, BOTH PILOTS "NOTICED SMOKE BILLOWING INTO THE COCKPIT". CREW DECLARED AN EMERGENCY AND REQUESTED AN IMMEDIATE RETURN TO ORD. THE SMOKE/FUMES BEGAN TO DISSIPATE DURING THEIR APPROACH AND FLIGHT MADE A NORMAL LANDING. AFTER LANDING THE PASSENGERS DISEMBARKED USING THE THE PAX ENTRY DOOR AND WERE TAKEN BY BUS TO TERMINAL.
BECAUSE OF THE COLD TEMPERATURE, ONE OF THE FLIGHT ATTENDANTS SUFFER A LITTLE FROSTBITE TO A FINGER WHILE HOLDING AN O2 BOTTLE. SHE WAS TREATED ON THE SEEN BY EMT(S).
MAINTENANCE PERSONNEL ARRIVED AND NOTICED A STRONG ODOR OF DEICE FLUID WHEN RUNNING APU BLEED SYSTEM WHICH DISSIPATED AFTER 15-20 MINUTES OF RUNNING THE PACKS.
IT APPEARS THAT DURING THE DEICING/ANTI-ICING PROCESS, FLUID WAS INJESTED INTO THE APU AND INTO THE BLEED/CONDITIONED AIR SYSTEM OF THE AIRCRAFT CAUSING SMOKE/FUMES.