BRIDGTON — A Casco woman was killed at around 7 a.m. Monday when her minivan crossed the centerline of Route 302 and hit a school bus, Bridgton police said.

Jacqueline Ingalls, 74, of Casco, was pronounced dead at the scene of the crash near 566 Portland Road on Packard’s Hill, according to a statement from the Bridgton Police Department. She was the only occupant of the 1989 Plymouth minivan.

Driver Blair Watson, 62, of Naples and three students on the Lake Region School District bus were transported to Bridgton Hospital for nonlife threatening injuries, the statement said.

Police aren’t sure why the woman swerved over the centerline and struck the southbound bus. The crash in under investigation by the Cumberland County Sheriff’s Office. The highway around the scene was closed for about three hours.