Berkeley Heights Public Schools went into a lockdown Thursday.

Police say the lockdown was caused by a call from a concerned citizen who reported a "potential serious threat" at Governor Livingston High School.

As police were sent to the school, the call was escalated to an active shooter threat within the school. Responding officers quickly secured the property at the high school.

A person of interest was located later, and not determined to be a credible threat, police say.

Police soon after said students were not believed to be in danger. The school district's website echoed police, saying "all schools are safe."

Students were released from their schools incrementally, with all schools dismissed by 4:45 p.m.