Kaniva News reports the referee blew the whistle on the match after two minutes and 51 seconds.
Commentators said the Frenchman was clearly outclassed by Fa.
The victory in Columbus, Ohio, gave Fa his 17th win.
It was his fourth fight in the United States.
It allowed Fa, who is 12th in the World Boxing Organisation World heavyweight rankings, to add the WBO International belt to his WBO Oriental title.
Fa fought Ouatah during the Arnold Classic Bodybuilding Championships.
Fa is widely reported to be looking for a high profile clash with Joseph Parker, who is ranked sixth with the WBC.
Ouatah, 33, is a French–Algerian pro boxer who won a gold medal in the super heavyweight class at the 2007 African Championship in Madagascar.
He won a silver medal at the All African Games in Algiers and fought at the 2008 Olympics.