- 9 updates
Public schools in Los Angeles are to reopen on Wednesday after a terror threat authorities now believe to be a hoax.
More than 1,000 schools were closed after an email was sent to a school board member.
Hundreds of thousands of schoolchildren were sent home after a threatened attack "with bombs and assault rifles".
The email was routed through Germany but it is thought it originated locally.
It comes after 14 people were killed and 22 others wounded in the San Bernardino shooting two weeks ago.
The threat that led to the closure of all public schools in Los Angeles is most likely a hoax, federal officials said.
The officials, who asked not to be named, echoed an assessment by New York Police Commissioner William Bratton that the decision Los Angeles authorities took to shut the school system was an over reaction.
US Congressman Adam Schiff, the top Democrat on the House Intelligence Committee, later said that a preliminary assessment suggests the emailed threats to New York and Los Angeles school districts were a hoax.
Schools in LA will remain closed as an investigation continues into the terror threat, police have said.
A LA police spokesman told a press conference: "None of our schools will be reopened until we are completely satisfied that we have taken every measure possible to ensure the safety of our students."
LA mayor Eric Garcetti has said the decision to close schools was made "in an abundance of caution."
The email threat to LA schools was sent to a board member from an IP address in Frankfurt, Germany, a school district spokesperson told Reuters.
New York City officials said they received the same threat that has closed LA schools but concluded it was a hoax.
Mayor Bill de Blasio said Tuesday morning that he was "absolutely convinced" there was no danger to schoolchildren in New York.
NBC reported the New York Police Department said a specific but non-credible threat was made to schools in New York this morning
"We don't see this as a credible terrorist threat," NYPD said.
All schools in the Los Angeles Unified School District are being searched to make sure they are safe.
More than 1,000 schools in the area were shut on Tuesday after an "electronic threat" was made against "many schools".
Ramon Cortines, the superintendent of LA schools, said: "I want every school, every early education centre, every adult school, I want them searched and a report made to me and the board of education that it is safe."
An "electronic threat" to many schools sparked the closures in the Los Angeles Unified School District on Tuesday.
The electronic threat came via a message, Ramon Cortines, the superintendent of Los Angeles schools said.
Officials said they were not aware of any other threats.
"In an abundance of caution as superintendent, Cortines has indicated we have decided to close our schools today until we can be actually certain that our schools are deemed safe," Los Angeles School Police Chief Steven Zipperman said.
More than 1,000 schools in the Los Angeles area have been forced to close due to a "safety threat".
All schools in the Los Angeles Unified School District were ordered to shut because of the threat.
Around 640,000 students go to school in the area, from kindergarten through to 12th grade.
The FBI has been notified of the threat, the validity of which is still being investigated.
Teachers were asked to stay at home, with employers urged to show the "maximum possible flexibility".