Officials with the Bonita Unified School District sent a message to families overnight about social media posts containing unspecified threats against schools in the La Verne and San Dimas areas.
The investigation revealed that the post "originated in schools in San Bernardino County last week," district officials said.
"Although the departments continue to investigate, they have determined that at this time there is no evidence that the posts are credible," the message read.
As a precaution, the sheriff's department deployed extra deputies to Lone Hill Middle School and San Dimas High School on Tuesday. La Verne police officers were deployed to Ramona Middle School.
There was also an increased police presence at the Bonita High School campus in La Verne.
"Late last night a social media post warning students 'not to go to BHS tomorrow' was brought to the attention of school administration and immediately reported to La Verne Police Department (LVPD). LVPD worked throughout the night and continues to actively investigate the post," read a message sent Tuesday morning.
Over in Burbank, the police department said it was aware of a social media post about a "perceived school threat." Authorities said the same message has been circulating in neighboring school districts but that "there is no evidence to suggest the threat is credible."
Meanwhile, Walter Reed Middle School in North Hollywood was briefly placed on lockdown Tuesday. According to a message from the school's assistant principal to parents, it was "connected to previous messages sent regarding the unfounded threat."
The school then resumed normal operations and students and staff were said to be safe.
In a follow-up note sent to Reed Middle School parents, the school's interim principal said the school was briefly placed on lockdown after a student reported seeing a social media post that mentioned threats to schools in the San Fernando Valley. The supposed threat tied to this post had already been deemed unfounded by law enforcement, the principal said, adding that mental health support is available to students if needed.
The Los Angeles School Police Department released the following statement saying the agency is aware of the social media threats:
In Santa Ana, Santa Ana police cleared the Mcfadden Institute of Technology campus following a threat of a possible active shooter. Officers conducted a thorough sweep of school grounds and said they found no threats.
"There are no reports of injuries, gunfire, or individuals with weapons. The school is being evacuated as a precautionary measure," Santa Ana police said in a statement posted on X.