AUSTIN (KXAN) — A teenager who drowned while swimming in Lake Travis earlier this month had carbon monoxide in her system, according to the Travis County Medical Examiner’s Office.

Sarah Pool, 15, was attending a church and wakeboarding camp near Volente Beach on June 11 when she fell into the water. Search crews recovered her body a few days later.

On Monday, a spokesperson for the Travis County Sheriff’s Office said Pool was not wearing a life jacket and it appears she was holding onto the platform on the back of the boat with two other girls when she went under.

While the investigation is still ongoing, authorities believe her death will be classified as a drowning.

The CDC has information on how to prevent CO poisoning on boats.