STANISLAUS COUNTY (CBS13) — A school bus driver in Stanislaus County was arrested for DUI Monday after a concerned student called 911.

The CHP says a student on the bus called 911 after noticing the bus driver was driving recklessly. Officers caught up to the school bus in the Diablo Grande Community neighborhood on Morton Davis Road around 2:45 p.m.

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They say the bus was stopped and they contacted the driver, Karolyn Denise Ray. A CHP spokesperson said Ray failed a field sobriety test and was arrested. Officers believe she was under the influence of a controlled substance.

The children on the bus, who ranged from kindergartners to fifth-graders, were all unharmed and released to their parents.

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Officials say Ray worked for First Students, a contracted company used by a local school district.