Two Mississippi Mills residents were involved in a serious all terrain vehicle (ATV) accident on July 24. The 19 year old woman and 21 year old man lost control of the ATV and went into a ditch. Both were thrown from the ATV. Neither wore a helmet. Witnesses to the accident brought the victims to hte Almonte General Hospital.The 19 year old driver sustained serious injuries and was transferred to Ottawa Civic Hospital. The 21 year old passenger also sustained serious injuries. Police are investigating the accident.