An anonymous social media post threatening Loyola High School in Harvard Heights prompted campus officials to cancel classes Wednesday.
The school was notified of the post Tuesday night. School officials said they canceled classes and on-campus activities as a precautionary measure "in collaboration with the FBI and the LAPD."
Authorities said the threat appeared to come from overseas, according to KABC-TV Channel 7.
"It was directed at a Loyola school, towards an unknown teacher, and ... the person appeared to be upset about a bad grade,'' Los Angeles Police Department Capt. David Kowalski told the station. "Currently, they're working it out, to try to determine where it's sourced from, and we work closely with the administrators at the school, to ensure that all the families and students feel safe coming back to school."
It was not immediately clear where the threat was posted.
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1:35 p.m.: This article was updated with comments from the police.