AUSTIN, Texas (AP) -

One student has been transported to a hospital after a fire extinguisher discharged aboard an Austin Independent School District bus.

Austin ISD spokeswoman Tiffany Young said the incident happened Wednesday morning while the bus was en route to Sanchez Elementary School.

Young had no immediate information on what caused the fire extinguisher to discharge on the bus carrying 27 students.

Austin-Travis County EMS officials say four children were evaluated at the scene. One of those students was transported for treatment of minor injuries related to possible exposure to toxic materials.