(RNN) - The Los Angeles Unified School District has closed schools Tuesday after what police called a credible threat.
A bomb threat was called in to an unidentified board member, according to the Los Angeles School Police Department. The Los Angeles Police Department and FBI are aiding the investigation.
School police chief Steve K. Zipperman said the threat was made electronically and mentioned the safety of the schools. Officials were still analyzing the threat early Tuesday morning.
Superintendent Ramon Cortines has asked police to search each of the more than 1,000 schools in the district by the end of the day to make sure they are safe.
"I think it is important that I take the precaution based on what has happened recently and what has happened in the past," Cortines said. "I want every school searched to make sure that it is safe for children and safe for staff to be there on Wednesday. I will issue a statement late this afternoon after the chief has informed me that schools have been searched and it is OK."
LAUSD is the second-largest school district in the nation and serves more than 640,000 students from kindergarten through 12th grade, according to its website. There are 900 public schools and 187 charter schools.
Students and staff have been directed to stay away from all campuses.
"We need families and neighbors to work together with our schools and with our employees to make sure our kids are safe throughout the day," LAUSD President Steve K. Zimmer said. "We need employers to show the flexibility that a situation like this demands; and we ask you to show the maximum possible flexibility with your employees who are primarily mothers, fathers and guardians today in this situation."
Some children were already on buses headed to schools when the call came, and the superintendent expressed concern about students who walk to school and could not be quickly contacted.
Cortines said the district receives threats "all the time," but he cited nearby San Bernardino and the mood of the country as contributing factors for shutting down the schools.
The mass shooting in San Bernardino, 60 miles from downtown Los Angeles, took place on Dec. 2. Syed Rizwan Farook and his wife, Tashfeen Malik, opened fire on Farook's coworkers at a holiday party, killing 14 and injuring 22.