Los Angeles orders public schools closed over unspecified threat

The US city of Los Angeles ordered all public schools closed Tuesday due to an unspecified electronic threat targeting the school system and its 640,000 students, officials said.

Ramon Cortines, the superintendent of Los Angeles schools, said he ordered the shutdown after police alerted him to a threat "made to not just one school, but many schools in this school district."

The Los Angeles unified school district tweeted: "LAUSD schools are closed today due to credible threat."

Police and FBI agents were called in to help search the more than 1,000 schools in the district, Cortines told a news conference, adding that he expected the operation to be completed by the end of the day.

The superintendant said the extraordinary measure was triggered in part by the December 2 attacks that killed 14 people in nearby San Bernardino.