A TWO VEHICLE ACCIDENT THAT SENT THREE PEOPLE TO THE HOSPITAL REMAINS UNDER INVESTIGATION BY MARSHALLTOWN POLICE.  THE ACCIDENT OCCURED MONDAY AT THE INTERSECTION OF SOUTH CENTER STREET AND SOUTHRIDGE ROAD, AND TRAFFIC WAS BLOCKED FOR SEVERAL HOURS TO ASSIST IN THE INVESTIGATION.  THREE PEOPLE WERE TAKEN TO UNITY POINT IN MARSHALLTOWN, AND ONE WAS SUFFERIG FROMWHAT WERE TERMED SIGNIFICANT LIFE THREATENING INJURIES.  NO IDENTITIES ARE BEING RELEASED AS THE ACCIDENT REMAINS UNDER INVESTIGATION.