TISHOMINGO, Okla. — A horrific crash, that killed six high school girls in Oklahoma two years ago, leads the head of the U.S. National Transportation Safety Board to warn parents on marijuana use.

Chairwoman Jennifer Homendy released a final report on the crash Thursday that says marijuana buds were found in the car that crashed into a semi in Tishomingo in 2022.

The board determined that the crash was caused by the 16-year-old driver slowing for an intersection, then accelerating through a stop sign because she likely was impaired by recent marijuana use and was distracted by having five teen passengers in the car.

OHP troopers said three of the girls killed were 15, one was 16 and two were 17. They all attended Tishomingo High School. The 16-year-old driving the car along with the other front seat passenger were wearing seatbelts. The girls in the back were not.

Chairwoman Homendy wants parents to talk to their children about the risks of driving after using marijuana.

“The lesson from this tragedy is painfully clear: marijuana is an impairing substance, period—and it’s a lesson we can’t afford to wait until driver’s ed to teach,” said NTSB Chair Jennifer Homendy. “We’re already behind when it comes to traffic safety, and marijuana-impaired driving is exacerbating the crisis. States have to do a better job of protecting road users from impaired drivers, regardless of the substance or its legality.”

The NTSB issued new safety recommendations focused on ensuring teens drivers are taught about the dangers of marijuana-impaired driving as part of their driver and classroom education and made additional recommendations for measures that can help reduce crashes that involve drug impairment.