ROCK VALLEY, Iowa (AP) -- School officials say no one was seriously injured when a school bus tipped over on a gravel road while picking up students near Rock Valley in northwest Iowa.

Rock Valley Superintendent Chad Janzen says there were nine students on the bus when the accident happened about 8 a.m. Wednesday. Janzen says most of the injuries were "nicks and bruises," but one student was taken to a hospital as a precaution. The bus driver wasn't hurt.

Janzen says the bus had picked up two students and wasn't going very fast when it went off the road and tipped over in a ditch. The cause of accident in under investigation.

Janzen says the students ranged in age from preschoolers to ninth graders.