LOS ANGELES -- Classes were canceled Tuesday for the Los Angeles Unified School District after what the district's superintendent called a "rare" threat that comes amid new concerns about security nationwide.
An "electronic threat" received early Tuesday prompted the decision, school district police Chief Steve Zipperman said, adding that the threat "is still being analyzed."
District superintendent Ramon Cortines explained the "message" referred to backpacks and "other packages." He said many schools were threatened, though none by name. The threat was toward students in schools (as opposed to on buses).
The threat came in an email to a school board member, school district representative Shannon Haber said.
Cortines noted his school district often receives threats. While he didn't go into detail, he said recent events -- such as this month's massacre in nearby San Bernardino, California; the Paris terror attacks; and heightened concerns about potential terrorism across the United States -- factored into the cancellation.
"The circumstances in the neighboring San Bernardino, I think what has happened in the nation, I think what happened internationally" played into the decision, Cortines said. "I, as superintendent, am not going to take the chance with the life of students."
The superintendent said he's asked authorities to search all of the roughly 900 charter and K-12 schools in his district "before the day is over." He promised a statement Tuesday afternoon that could offer more information about what prompted his decision and lay out what will happen next, including whether classes will be in session Wednesday.
That won't happen, Cortines insisted, "until I know it's safe."
Some already at schools when closures announced
On any given day, running the Los Angeles Unified School District is a complex operation. It has more than 650,000 students enrolled in kindergarten through 12th grade, with some 250,000 more in adult education programs.
Educators are tasked not only with teaching lessons, but nurturing a safe, positive school environment. Then there's the matter of getting students to and from school as efficiently as possible.
These challenges grew even more complicated when Cortines announced the school closures around 7:15 a.m. PT (10:15 a.m. ET) Tuesday. By then, some facilities had opened, and some students and staff were already there, with others on the way. They've all since been asked to go home or, in the case of children, stay under an adult's watch until someone can come get them.
To help, the Los Angeles public transit system offered students with valid IDs a free ride home through noon Tuesday.
Cortines pointed out that district schools often go into lockdown in response to nearby real or potential dangers. The threat in this case was "not to one school, two schools, three schools. It was many schools, not specifically identified."
"That's the reason I took the action that I did," he said.
New York police think similar threat a 'hoax'
New York Police Commissioner Bill Bratton said a superintendent in his city's school system -- the country's largest -- received an email "almost exactly the same" as one sent to Los Angeles.
New York police think it is a "hoax," not a credible threat, according to Bratton. The message is believed to have originated overseas but does not seem tied to a jihadist initiative, the commissioner said, noting Allah -- the Arabic word for God -- is not spelled with a capital A.
Haber, the Los Angeles school representative, said the email threat to that district appeared to have come from Frankfurt, Germany.
The FBI is working with New York as well as Los Angeles police on the threat, according to Bratton.
Calling the writing generic, New York Mayor Bill de Blasio said it's important that people don't overreact.
"(It would be a) huge disservice to our nation," the mayor said, "to close down our school system."
Los Angeles mayor grateful for 'abundance of caution'
In Los Angeles, city leaders rallied behind Cortines' decision to call off school because of the threat.
Mayor Eric Garcetti noted how the San Bernardino attack had changed the dynamic in Southern California. "An abundance of caution is something that ... all of us who have children can appreciate," Garcetti said.
"We will continue to hope that this is nothing and that our children can be back at school tomorrow. But as a parent and as a mayor, certainly, I'm here to support this school district."
Cortines told reporters later Tuesday he took action after consulting with other top school officials and the head of the school district's police. After that, Los Angeles police got involved and "connected some of the dots nationally on this," according to Garcetti.
"There are no secrets," Cortines said. "Somebody has sent information that leads us to pause and make sure that ... our children and our staff is safe."