All school campuses in the Los Angeles Unified School District (LAUSD) were shut after the a school board member received an unspecified threat, said reports.
Searches are underway in the local schools after the Los Angeles Police Department (LAPD) and the Federal Bureau of Investigation were notified.
The authorities have decided to close all the schools as the electronic threat was made to numerous but unspecified campuses. The threat message had reportedly mentioned backpacks and other packages.
"I think it's important to take this precaution based on what has happened recently and what has happened in the past," Los Angeles Times quoted LAUSD superintendent Ramon Cortines as saying.
"This is a rare threat. It was not to one school, two schools or three schools, it was many schools," he added.
The threat comes after 14 people were recently killed by a Isis-linked Muslim couple in San Bernardino, which is also comes under the state of California.
The officials said the schools will remain closed until it is made sure that the area is safe.
LAUSD is the the second largest district in the United States, with over 6.4 lakh students in across 1200 schools. This is the first closure of the whole district in a decade.