LAKEVILLE (AP) — A Minnesota school district is being sued by the parents of two high school students killed in a 2015 car crash who allege school officials failed to protect the teens from an off-campus game called "Nerf wars."

Lakeville South High School students Jacob Flynn, 17, and John Price, 18, died in December 2015 after being thrown from a pickup truck that crashed. The driver and another passenger survived. Law enforcement officials said the "Nerf war" game was a factor in the accident.

Students who play the game shoot other teens with the soft Nerf projectiles to score points and win money. According to the game's rules, schools and places of worship were safe zones, so students would "kidnap" others after school hours and take them elsewhere to shoot with the spongy missiles.

The lawsuit said school administrators knew about the aggressive behavior associated with the game, but didn't take action to stop it. The suit was filed against Lakeville Area Public Schools, a district in the southern Twin Cities suburbs.

"They knew that kids were getting hurt. They knew this was escalating," said Greg Walsh, the families' attorney. "They had an opportunity to protect the kids from a known danger and they failed."

The lawsuit said it was commonplace for students to be forcibly kidnapped from the school parking lot after dismissal. It also cited an email sent to administrators by the school's activities director that expressed concern about the Nerf game two months before the crash.

Walsh said school districts have been held liable in similar situations for student injuries during off-campus activities that were known to administrators.

At the time of the crash, no charges were filed. Dakota County prosecutor James Backstrom said the teens were willing participants in the game.

The school district released a statement Thursday saying they continue to grieve for the loss of Flynn and Price, but there is no liability or fault on behalf of Lakeville Schools.