Firefighters who responded to the scene said an object that was six-feet wide and 12- to 15-feet long fell and hit people just before 2 p.m. The object was hanging from the ceiling in the recently remodeled food court area.
Ten people were injured, but only seven were taken to a local hospital. Authorities described most of the injuries as minor.
"I saw a guy that was like laying on the ground, got cracked in the head pretty hard," said Danny Badillo of Rancho Cucamonga.
Ontario Mills General Manager Marc Smith said in a statement, "A small piece of the architectural drop ceiling fell ... We are thoroughly investigating this matter as we remain committed to the safety of our shoppers, retailers and employees."
It was unclear if the recent renovations had anything to do with the accident.