COLUMBIA COUNTY, Wis. (CBS 58) -- The man accused of crashing a semi into a school bus filled with students has pleaded not guilty to felony charges. 

Police say 42-year-old Wayne Murphy drove under the influence of prescription medications when he crashed into the bus, injuring 20 people back in May. 

The bus was carrying students from Milwaukee's Hope Christian School. It was pulled over because of mechanical problems. Murphy is due back in court in November.