Investigators are on scene at the Priest Rapids Dam in Grant County after an explosion happened Thursday around 4:00 p.m. According to Kyle Foreman of the Grant County Sheriff's Office, five employees were injured in the explosion. By 6:10 p.m. the number of reported injured had increased to six. All of the patients were taken to Harborview Medical Center in Seattle to be treated for burn injuries. One victim was released from the hospital Friday morning. Officials said two of the patients are listen in critical condition, and the remaining three are in satisfactory condition. They arrived shortly after 10:00 p.m. Thursday. Thomas Stredwick of the Grant County Public Utility District said all of the injured are employees of Grant PUD. He said they are power plant electricians and operators. "This is a difficult day for everyone here at Grant PUD," said CFO and Acting General Manager Kevin Nordt. "Our primary focus will continue to be taking care of our people."