HARTLAND TOWNSHIP, Mich. (AP) — Authorities say injuries from the weekend crash of a charter bus carrying Michigan middle school students returning from a Chicago-area music trip included a broken neck and broken ribs.

The Livingston County sheriff’s office initially believed injuries were relatively minor from the Saturday night crash on an Interstate 96 ramp in Howell Township, about 45 miles northwest of Detroit. The department said Monday, however, that some of the 17 people taken to hospitals had serious injuries.

The bus carrying more than 40 Hartland Middle School students, teachers and chaperones went off the roadway and tipped over. Other injuries included a collapsed lung and a broken hand.

The investigation into the cause continues this week with interviews of passengers. The Livingston County prosecutor’s office will review the results.