Responding to a threat emailed to school board members and campuses, all Los Angeles Unified School District campuses were closed Tuesday and authorities conducted an exhaustive search of more than 900 schools, but a congressman said the threat appears to be a hoax.

“While we continue to gather information about the threat made against the Los Angeles and New York school districts, the preliminary assessment is that it was a hoax or something designed to disrupt school districts in large cities,” said Rep. Adam Schiff, D-Burbank and the ranking member of the House Permanent Select Committee on Intelligence.

State Superintendent of Public Instruction Tom Torlakson said Tuesday he supports the decision to close Los Angeles schools in response to an email threat, and he directed his staff to work with the district to prevent the loss of potentially millions of dollars in state funding due to the mass closure.

Torlakson said he instructed state Department of Education officials to work with the Los Angeles Unified School District so it can qualify for relief from a loss of Average Daily Attendance funding from the state. The amount of money schools receive from the state is based in part on how many students attend class on a daily basis. A drop in attendance leads to a drop in funding—and a full closure of the district for the day could be particularly costly.

According to the state, a district can receive special ADA credit for days lost due to an “emergency closure.”

LAUSD officials announced shortly before 7 a.m. that all schools would be closed for the day in response to the threat, which made reference to bombs, weapons and other destructive devices that had allegedly been planted on campuses throughout the district.

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 specifically referenced the Dec. 2 terrorist shooting in San Bernardino as contributing to his decision.

A similar threat was also received by schools in New York City, but officials there concluded that the threat was not credible, and they allowed schools to open as normal. New York Police Commissioner Bill Bratton, former chief of the Los Angeles Police Department, said LAUSD’s decision to shutter all campuses was a “significant overreaction.”

Los Angeles officials, however, including Mayor Eric Garcetti and LAPD Chief Charlie Beck, stood by Cortines’ decision, calling the safety of children a top priority.

There was no immediate word on whether schools would reopen Wednesday. School Police Chief Steve Zipperman said the campuses would remain closed until they are deemed to be safe.

The LAUSD closure applied to all campuses—more than 900 of them. The district is also home to about 200 charter schools that were also affected, along with dozens of educational centers. The district, the nation’s second biggest, serves an estimated 700,000 students. Most other Southland schools outside the LAUSD remained open, although some Catholic schools run by the Los Angeles Archdiocese were closed because of their proximity to LAUSD campuses. Diocese officials said that decision was being left to individual school principals.

LAUSD officials would not provide specifics of the threat, which was initially reported by police to have come via telephone, but was later revealed to have come in via email, apparently either from or routed through Frankfurt, Germany. Beck said late Tuesday morning that officials believe the email likely originated from somewhere much closer than Germany.

Rep. Brad Sherman, D-Sherman Oaks, said he saw the email, and said 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,” he said. “The email makes relatively specific and wide-ranging threats to Los Angeles schools. We do not know whether some or all of the threats are truthful.”

Sherman said the email referenced bombs or possible nerve agents and suggested there were about 32 people involved in possibly planting the devices.

“The text of the email does not demonstrate that the author has studied Islam or has any particular understanding of Islam,” Sherman said.

Bratton told reporters in New York that the threat received there

mentioned “Allah,” but the word wasn’t capitalized—providing a clue that the threat might be a hoax.

Beck said, however, the email contained very specific threats aimed at the LAUSD. He had strong words for anyone who might criticize Cortines fordeciding to close the schools, saying the “safety of our children” is the highest of priorities.

“These are very high stakes,” Beck said.

Garcetti also threw his support behind Cortines. “The decision to close the schools is not mine to make, but it is mine to support as the mayor of Los Angeles,” Garcetti said. He said decisions need to be made “in a matter of minutes” and it’s unfair to be critical of Cortines when the safety of children is at stake. The mayor also said the email threatened that weapons were already in place at campuses.

Schiff, in announcing that the threat appears to be a hoax, did not weigh in on the propriety of closing the nation’s second-largest school district—creating the type of disruption that is the primary goal of terrorists.

“The safety of our communities and particularly our young people is paramount,” Schiff said. “At the same time, in an environment in which it is very easy to transmit threats, real and otherwise, and when fear and disruption may be the goal as well as the effect, communities and law enforcement will need to make a difficult judgment as to how to respond in a variety of circumstances.”

Parents were told to keep their kids at home and retrieve those already taken to school by meeting them at the campuses’ reunion gates.

Cortines said he ordered all campuses to be searched—a monumental task in such a widespread district. Cortines said he ordered the closures because he was not going to take a chance given recent terror strikes in Paris and San Bernardino.

“I think it’s important to take this precaution based on what has happened recently and what has happened in the past,” Cortines said early Tuesday, speaking less than two weeks after a couple—a U.S. citizen of Pakistani background and his Pakistani wife—killed 14 people in San Bernardino in the deadliest terror strike on U.S soil since 9/11.

The LAUSD closures came on a day when finals were scheduled at high schools, leading some students to speculate that a student fearing exams was involved, according to broadcast reports.

The LAUSD set up an information hotline for parents at (213) 241-2064.

The bulk of other Southland school districts announced that classes were continuing as normal, although some, such as Pasadena, said they would have stepped-up security on campuses.

The two high schools run by the Los Angeles County Office of Education—the High School for the Arts on the Cal State Los Angeles campus and International Polytechnic High School on the Cal Poly Pomona campus—remained open. The LACOE did not receive a threat and determined that both locations were safe for students, according to LACOE spokeswoman Margo Minecki.

Minecki said another high school on the Cal State LA campus—Alliance Marc and Eva Stern Math and Science School—was closed because it is part of the LAUSD system.

“We have not heard reports of any other closures” from the other 79 school districts in the county that the LACOE supports, Minecki said. However,she cautioned that those districts are independently run and would not necessarily reach out to the LACOE to report closures.