The Harris County Sheriff's Office responded to the wreck at about 12:21 p.m. in the 4000 block of Holy Road, near the Crosby area.
Sheriff Ed Gonzalez initally said it appeared three people were ejected in the crash. In a later update, Gonzalez said two occupants riding on the outside of the truck jumped off when the vehicle started to roll.
Life Flight was requested for the truck driver, Gonzalez added. The other two victims were taken by ground ambulance.
Drivers were urged to avoid the area as the investigation continued.
It's still unclear what may have led to the crash.