HOUSTON — Two students were killed and three other people seriously injured when a school bus rolled off a Houston freeway overpass.

A Houston Independent School District statement said a girl died at the scene Tuesday morning, and another student died at a hospital.

The district said two other students and the bus driver were taken to hospitals with serious injuries.

The bus was bound for Furr High School, which also operates a charter school.

Names of the victims haven’t been released.

Officials were investigating the cause of the crash. District spokeswoman Ashley Anthony said the bus apparently drove off an overpass. Guardrails were damaged. The bus rolled and landed on its side.

Houston operates the state’s largest public school district with about 215,000 students.