Authorities continue to investigate the cause of a school bus fire that killed two people in western Iowa Tuesday morning.The fire was reported at 7:02 a.m. Tuesday at 17840 480th Street, just southeast of Oakland in Pottawattamie County. Two people on the bus, from the Riverside Community School District, died in the fire, according to the Pottawattamie County Sheriff’s Office — the driver, Donald Hendricks, 74, of Carson, and a passenger, Megan Klindt, 16, of rural Pottawattamie County.No one else was on the bus at the time of the fire, officials said.