What we know so far, per the Los Angeles Times:

Officials closed all Los Angeles Unified School District campuses Tuesday morning after receiving a “credible threat” of violence involving backpacks and packages left at campuses.
Authorities said they plan a search operation of all of the LAUSD’s more than 900 schools. The nation’s second-largest school district has more than 700,000 students. . . .
Fearing the safety of schools and students, [LAUSD Superintendent Ramon] Cortines said he couldn’t take a chance, so he asked police to search all campuses, adult school and early education centers before reopening Wednesday.
Officials said the threat came in electronic form and was made to numerous but unspecified campuses.

The nature of the threat is still unclear. According to NBC Nightly News, a bomb threat was emailed to a school board member.

Stay tuned to The Corner for further updates.