Packed bus hits overpass pillar

One person was killed and several were injured after a Megabus crashed in Illinois, Thursday.

• NEW: The Megabus coach hit a pillar on Interstate 55, the company says
• NEW: One person was killed and about two dozen were sent to hospitals
• The Megabus coach crashed near Litchfield, Illinois
• The cause of the crash is under investigation, police say

(CNN) -- One person was killed and as many as two dozen were injured when a commercial bus crashed into an overpass pillar on a southern Illinois interstate, authorities reported Thursday.

The Megabus coach line said there had been one fatality among the 81 ticketed passengers aboard its Chicago-to-St. Louis bus. The wreck occurred near Litchfield, about 55 miles northeast of St. Louis, the Illinois State Police told CNN.

"Safety remains our No. 1 priority," the company said. "The thoughts and prayers of our entire staff go out to the passengers involved."

The injured were being taken to hospitals in Litchfield and nearby Staunton. Paula Endress, a spokeswoman for St. Francis Hospital in Litchfield, said the 13 patients taken there had injuries ranging from minor to grave. And Susan Campbell, CEO of Staunton's Community Memorial Hospital, said that facility had taken in three patients and expected as many as nine more.

The cause of the crash was under investigation, police said.

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CNN's Rich Porter and Amanda Watts contributed to this report.