A large decorative helicopter fell from the ceiling into a swimming pool below while people were in the water. It happened just after 3 p.m. Sunday.
The mall says the injuries were minor, but one of the four people was taken to the hospital. The rest of the injured left on their own.
American Dream released a statement saying they will conduct an investigation to "ensure the park meets all safety regulations as required."
Police say the water park was evacuated after the incident.