WASHINGTON, June 15 (Xinhua) -- Two riders from a roller coaster derailment in the U.S. state of Florida are still in hospital, a spokesman said Friday.

Nine passengers were taken to Halifax Health Medical Center after Thursday night's derailment of the Sand Blaster coaster on the Daytona Beach Boardwalk, according to the hospital.

Five of them were discharged Thursday night, and another two were discharged Friday morning.

The derailment sent two riders plummeting about 10 meters to the ground, with eight others requiring rescue.

Investigators are examining the cause of the incident. Local reports said the roller coaster passed a state inspection hours before the derailment.