DENVER -- A multi-vehicle accident closed two lanes of westbound Interstate 70 Friday afternoon as people headed into the mountains for the weekend.

A school bus was one of the vehicles involved. It had a large gash in the side, apparently caused by an axle that came off a pickup truck. Another vehicle had clearly burned. Wreckage was spread across the highway for about a half mile just east of the Genesee exit.

All three lanes of westbound I-70 were blocked for several hours Friday afternoon and traffic was backed up nine miles to Ward Road in the westbound lanes.

A Flight for Life medical evacuations helicopter landed on the interstate to airlift the most seriously injured person to the hospital. Another injured patient was taken by ground ambulance. Both patients were listed in serious condition.

Students from the Roaring Fork School District bus were standing on the side of the highway after the accident. There were 16 students from Basalt, Colo., High School and three adults on board the bus when it was hit. None of them were seriously injured, although some were cut.

The female students played in a 3-A soccer match in Golden Thursday night and were returning to Basalt.

The accident apparently began when a car from the eastbound lane crossed the median and went into the westbound lane, causing a chain-reaction accident.