(Olympia, WA)  --  A formal complaint is being lodged by the state of Washington against the Ride the Ducks tour firm in Seattle, after one of the company's amphibious vehicles was involved in a crash that killed five people and injured dozens of others.  The complaint has been filed by the Washington Utilities and Transportation Commission, which says the vehicle was operated in an "unsafe manner."  Earlier this week, the commission suspended operation of all Ride the Ducks amphibious vehicles.   The "Seattle Times" reports the commission may allow some of the company's smaller Duck vehicles to return to service within a month, pending state inspections.