LOS ANGELES- All schools in the vast Los Angeles Unified School District have been ordered closed due to a threat.

A law enforcement official says the threat that closed all schools in the vast Los Angeles Unified School District was emailed to a school board member and appeared to come from overseas.

The official spoke on condition of anonymity because he was not authorized to speak publicly about the investigation. The official says the threat was sent late Monday.

Superintendent Ramon Cortines says the threat was made against students at many of the district's schools. Officials wouldn't elaborate.

Cortines says the San Bernardino shooting that left 14 people dead on Dec. 2 influenced the decision to shut down the district's more than 900 schools and 187 public charter schools.

School district spokeswoman Ellen Morgan announced the closure Tuesday but released no further details ahead of a press conference at district headquarters.
    
The district, the second largest in the nation, has 640,000 students in kindergarten through 12th grade and more than 900 schools and 187 public charter schools.
    
The district spans 720 square miles including Los Angeles and all or part of more than 30 smaller cities and some unincorporated areas.