A chain-reaction crash shut down a Missouri highway Saturday after a Greyhound bus slammed into a tractor-trailer and caused a 25-vehicle pileup west of St. Louis, authorities said. Elsewhere on the same interstate two people were killed in a crash as snow moved through the state. In the chain-reaction wreck, at least 25 vehicles crashed into one another after a Greyhound bus carrying 55 people rear-ended a tractor trailer on Interstate 44 near the town of Rolla, the Missouri State Highway Patrol said. Crumpled tractor-trailers and cars were seen scattered all over the roadway and in a ditch after the 1:30 p.m. crash.