This story is developing; we will provide more details as they become available.

Los Angeles schools have been shut down today after officials received a threat against “many” schools. According to a tweet from the Los Angeles Unified School District (LAUSD), the threat is considered to be “credible.”

Los Angeles Schools Closed For 'Credible' Threat Against Many Schools

Students at Los Angeles schools being sent home

All the students are safe at this time, according to another tweet from the school district, and those who have already arrived at school are being sent home. The buses that arrived at school are being sent back to return the students to their homes. School officials are also taking other measures to keep the students safe.

Law enforcement officers are searching all of the schools in the district, and the LAUSD is providing continuing updates on its Twitter account. The school district is the second biggest in the U.S. with 640,000 students in grades K through 12. The LAUSD administers over 900 schools and another 187 charter schools.

Bomb threat against Los Angeles schools

Although at first the nature of the threat against the Los Angeles schools wasn’t clear, The New York Times now reports that officials are saying that it’s a bomb threat and that it appears to be credible. It was received electronically, and the FBI and law enforcement officers are analyzing the threat.

The U.S. remains on edge after the recent terrorist attack in San Bernardino in which 14 people died and 22 were injured. Officials for the Los Angeles school district that although there have been multiple bomb threats over the last couple of weeks, this particular one caused them to be more concerned.

School District Superintendent Ramon Cortines said the threat was made against “many schools” in the district, although the specific schools that were being threatened were not named. He added that some of the details given in the threat mentioned backpacks and packages.