A Missouri college student is the third person to die after a major crash this week on Interstate 55 in southwestern Illinois.

The Belleville News-Democrat says Vivian Vu of Joplin, Missouri, died at a hospital Thursday, two days after a tractor-trailer crashed into many vehicles in Madison County. She was a student at Missouri Southern State University.

The 19-year-old Vu was returning to Missouri from Chicago with other students and a faculty member. They had attended a Model United Nations Conference.

Illinois State Police spokesman Calvin Dye says investigators are trying to determine why a 53-year-old trucker from Colorado didn't slow down or stop.

Two others killed in the crash were 20-year-old Hailey Bertels and her 17-year-old sister, Madisen Bertels, both from Staunton, Illinois. Dye says "it's a miracle" that more people weren't killed.

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