Amtrak has sued the trucking company that owned a tractor-trailer rig which slammed into one of its trains in Nevada last week in a fiery crash that killed six people and injured dozens of others. The passenger rail service, partly owned by the U.S. government, sued the John Davis Trucking Company in U.S. District Court in Nevada on Wednesday, seeking unspecified damages. Amtrak claims in court papers that the trucking firm was negligent in hiring driver Lawrence Valli, who it says was "incompetent and unqualified" to operate or maintain the gravel-hauling rig.