The US city of Los Angeles ordered all public schools closed today after receiving an unspecified threat targeting the school system and its 640,000 students, officials said.
"Earlier this morning we did receive an electronic threat that mentions the safety of our schools," Steven Zipperman, chief of the Los Angeles school police department, told a news conference.
"We have chosen to close our schools today until we can be absolutely sure that our campuses are safe," he said.
