The Allegheny County district attorney's office, which is part of the task force, is reviewing the materials.
The teacher was fired Friday for violating the code of employee behavior at Sewickley Academy, which has about 700 students from kindergarten through 12th grade. Officials there notified authorities and turned over the materials in conjunction with the firing.
School and law enforcement officials aren't identifying the teacher, who hasn't been criminally charged, or specifying the alleged wrongdoing.
The school says it also alerted the county's Child Welfare Services and Child Protective Services offices.
DA's spokesman Mike Manko says the investigation is ongoing.