Investigators with Fullerton police were investigating separate bomb threats at four schools Thursday.

The schools that were targeted in the threats were Sunny Hill High School, Fullerton Union High School, Troy High School and Fern Drive Elementary School.

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The four campuses were placed on lockdown as officers combed through the schools to confirm the validity of the threats. It was not immediately clear whether the threats were credible.

At Fern Drive Elementary, officers were on scene with students and staff while parents were advised to follow school district evacuation procedures.

It was not clear if anyone was injured during the investigations.

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