Background
The flight was approaching its destination airport when the pilot began deviating around thunderstorms. The pilot used airborne radar to identify severe cells, but due to the dark night, visual contact with the severe weather was not possible.
Cabin Preparations
Approximately 45 minutes before the turbulence encounter, the captain turned on the seat belt sign after encountering 'light chop' earlier in the flight. A public address announcement instructed passengers to return to their seats and fasten their seat belts. About 20 minutes before the event, the captain directed flight attendants to suspend service and secure the cabin. Another PA announcement advised passengers of an increased chance of turbulence during the remainder of the flight.
Turbulence Event
The aircraft encountered turbulence lasting a few seconds. One large 'bump' was accompanied by a sudden altitude gain that persisted for a couple of seconds. After the event, flight attendants reported injuries to several passengers. According to the flight attendants, one or more of the injured passengers were not in their seats at the time of the turbulence encounter.
Aftermath
No further details about the extent of injuries or subsequent actions are provided in the source.