The email mentioned if classes were canceled, there would be an attack on the streets of Los Angeles, San Bernardino, Bakersfield and San Diego.
Since the email did not specifically mention schools in San Diego, San Diego Unified School District directed FOX 5 to investigators.
“As soon as LA had it. I’d say within moments we knew. It is one of the things that came out of 9/11,” said San Diego County Sheriff's spokeswoman Jan Caldwell. “We had multiple agencies look into this and talking with other security agencies. We were able to ascertain pretty quickly that this was an unfounded threat.”
San Diego Mayor Kevin Faulconer's Office issued a statement about the threat:
“Unlike Los Angeles And New York City, a threat was not sent to San Diego officials. The email, which focused almost entirely on Los Angeles, referred to San Diego in passing along with other Southern California cities.”
“The San Diego Police Department and San Diego Unified school police did not believe the message posed a credible threat, but in an abundance of caution provided extra patrols at local schools. San Diego law enforcement will continue to coordinate with state and federal officials and remain vigilant.”
LAUSD students returned to their classes on Wednesday, one day after an emailed threat of violence that prompted an unprecedented districtwide closure was deemed to be "not credible."
Police had been expected to step up and increase patrols around LAUSD schools as the district's campuses reopened.
The threat against the nation's second-largest school district was sent to a school board member Monday evening. The Los Angeles Police Department was notified that night about the "specific" threat, which involved explosive devices and firearms, LAPD Chief Charlie Beck said.
Out of an abundance of caution, LAUSD Superintendent Ramon Cortines made the decision to close all schools for the day while plant managers and law enforcement personnel conducted thorough searches of all the district's campuses.
LAUSD serves more than 640,000 students throughout the Los Angeles area and in multiple nearby cities, according to its website. The district is made up of about 900 school and 187 public charter schools.