Authorities are investigating reports of an explicit sex video involving minors circulating among students at a Bucks County middle school.

The video was reported to show sexual conduct between two juveniles, Bristol Township police said in a statement distributed Wednesday.

The tape was circulating via cellphone among students at Franklin D. Roosevelt Middle School in Bristol Township, officials said.

"It's an unfortunate situation," said Samuel Lee, the Bristol Township schools superintendent.

In a letter sent Wednesday, Lee told parents: "It is my understanding that a video has been distributed among students which shows minors engaged in activities that are inappropriate and, in fact, illegal."

The letter said law enforcement and child welfare agencies had been notified.

Authorities said they do not believe the video was filmed on school property, and police have confiscated several phones as part of the investigation.

The superintendent urged parents to talk to their children about the risks of sharing explicit video.

"While the temptation to forward such a video from one friend to another could be on your child's mind, doing so is illegal when those involved are minors," the letter said. "It is essential that you make your child aware of this fact so that he or she does not run the risk of criminal charges."

The investigation into the video is ongoing.