Leslie Heilbron, the district's assistant superintendent, said she was notified Tuesday by law enforcement about the threat. She did not give any details about the nature of the threat, saying she was limited in the information she can offer in order to not compromise the law enforcement investigation.
All campuses, including all the summer activity camps, and the district office were shut down on Wednesday, Heilbron said.
Upon investigation, Ventura County sheriff's officials determined there was no immediate threat to any one person or school. The investigation was ongoing, though sheriff's officials deemed the threat as not credible.
Heilbron said the sheriff's department will increase patrols near the district's campuses out of an abundance of caution.
Sheriff's authorities said parents were notified about the threat and resulting closure in an email Tuesday evening.
The Oak Park Unified School District has yet to announce when the campuses will reopen.