All schools in the vast Los Angeles Unified School District have been ordered closed due to a threat, a spokeswoman Ellen Morgan said Tuesday.

During a press conference Tuesday officials said they received the electronic threat and were still analyzing it. They said the action was being taken out of an abundance of caution. Schools would remain closed until the threat was cleared, which they expected to happen by the end of the day.

"We need to cooperation of the whole of Los Angeles today," said school board President Steve Zimmer. "We need families and neighbors to work together with our schools and with our employees to make sure our schools are safe throughout today."

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.