(WPXI) – Seven students and a bus driver were taken to the hospital after a school bus for the Mars Area School District crashed into a tree in Butler County. The crash happened a little after 8 o’clock Thursday morning in the 1600 block of Three Degree Road in Adams Township. A mass-casualty incident was initially declared for crews to get enough EMS resources to the scene. Mars Area School District superintendent Dr. Mark Gross said the all students on the bus at the time of the crash were evaluated by medics, and their parents were contacted. UPMC says seven students were treated at various hospitals and one student remains hospitalized under observation. The bus driver’s condition is currently not known. That individual was taken to Allegheny General Hospital. Gross said students who were determined by medics to be “not injured” were placed on another bus to continue to school. When those students arrived, they were checked by the school nurse before going to class. Social workers and guidance counselors will be available for any students who need assistance on Friday even though it is an in-service day for students.