A barge raises a submerged car found in the sea near Wando, June 29. Yonhap

Police investigating the mysterious deaths of a 10-year-old girl and her parents found last month in a car sunk in waters off the southwestern coast said Wednesday that sleeping pill ingredients have been found in their bodies.

The Gwangju Nambu Police Station said it was recently informed by the National Forensic Service of the detection of sleeping pill ingredients in the remains of Cho Yu-na, a Gwangju elementary school student, and her parents in their 30s.

Cho and her parents, who resided in the southwestern metropolitan city of Gwangju, were found dead on June 29 inside their family car pulled out of waters off Wando, a quiet island about 120 kilometers south of their home. The family went missing about a month earlier after last being seen alive on closed-circuit TV at a Wando guesthouse on May 30.

Police have also restored the family car's event data recorder and black box.

Judging also from the black box dialogue between Cho's parents and the movement of the vehicle just before the accident, police have reportedly come to the tentative conclusion that the family may have taken their own lives. (Yonhap)