By CBS13 Staff

COLUSA COUNTY (CBS13) — A deadly head-on crash in Colusa County prompted the response of three helicopters to rush people to the hospital over the weekend, authorities say.

The crash happened Sunday night near the intersection of Highways 20 and 16.

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Exactly what led up to the crash is unclear, but first responders immediately declared it a mass-casualty incident. One person was pronounced dead while several others suffered major injuries.

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A total of three people were flown to the UC Davis Medical Center in Sacramento. Another patient was flown to Kaiser Hospital in Vacaville.

Few details about the victims have been released, but California Highway Patrol said some of the patients were juveniles.

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The cause of the crash is still under investigation.