LOS ANGELES (CBSLA.com) — More than 1,500 school buildings that were shut for a day after an emailed threat will reopen Wednesday, according to the Los Angeles Unified School District.

Mayor Eric Garcetti said the FBI has concluded it was not a credible threat.

An “electronic threat” that prompted the unprecedented closure of all of the district’s campuses Tuesday is believed to have been “a hoax or something designed to disrupt school districts in large cities,” according to Rep. Adam Schiff, a ranking member of the House Permanent Select Committee on Intelligence.

Police Chief Charlie Beck and Sheriff Jim McDonnell said patrols will be stepped up around the school campuses to help alleviate any anxiety among students and parents. The LAUSD also plans to have crisis counselors available on campuses.

“We invite all of our families, all of our kids, all of our teachers back into the LAUSD public schools tomorrow in the hope that we will never ever have to have another day like today,” LAUSD Board of Education President Steve Zimmer said.

Beck said the threat, which made reference to bombs, assault rifles and other weapons, was emailed to some school board members late Monday and was routed through Frankfurt, Germany. 

LAUSD is the second-largest school district in the nation, serving more than 655,000 students. The closure affected more than 900 campuses, plus about 200 charter schools and dozens of educational centers.

Zimmer said more than 1,500 educational sites were searched. Some Catholic schools run by the Los Angeles Archdiocese were also shut down because of their proximity to LAUSD campuses.

Superintendent Ramon Cortines said he made the unprecedented decision to close all school campuses out of an abundance of caution, saying that “based on past circumstances, I could not take the chance.” He referenced the Dec. 2 terror shooting in San Bernardino as being behind his decision.

The closure cost the school district $29 million. But Beck said Cortines made the right call. “Would you have sent your child to school? Every parent I’ve asked has said no, of course not.”

Rep. Brad Sherman, D-Sherman Oaks, said he reviewed the threat and says the author “claims to be an extremist Muslim who has teamed up with local jihadists. We do not know whether these claims are true or a lie. We do not know whether this email is from a devout Muslim who supports jihadists or perhaps a non-Muslim with a different agenda,” Sherman said.

He said the email referenced bombs or possible nerve agents and suggested there were about 32 people involved in possibly planting the devices. But “the text of the email does not demonstrate that the author has studied Islam or has any particular understanding of Islam,” Sherman said.

The threat against LAUSD comes a day after a bomb threat against San Bernardino Valley College. It was later determined to be a hoax also.

New York City officials say they received the same threat that led to the closure of LAUSD schools but quickly concluded that 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, and former LAPD chief and current New York Police Commissioner Bill Bratton said he thought Los Angeles officials overreacted by deciding to close the nation’s second-largest school district.

Bratton said the person who wrote the email claimed to be a jihadist but made errors, indicating that the individual is a prankster.

“It is very easy in hindsight to criticize a decision based on results that the decider could never have known. It is also very easy to criticize when you have no responsibility on the outcome of that decision,” Beck said.

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