New Milford Police hope to have a preliminary cause determined by next week of a fatal Route 7 crash involving a passenger car and a dump truck.  Monday's accident by Ceder Hill remains under investigation and Police say they're not releasing details on certain aspects of the incident at this time.  The state Medical Examiner's Office says 24-year old Christina Walters died of blunt impact of head, torso and upper extremities with fractures and visceral injuries.  Her death was ruled accidental.  The dump truck driver, 56-year old Jeff Griener, was released from the hospital.  He was able to wade to shore after his truck went down an embankment and became partially submerged in the Housatonic River.