Educators and law enforcement officials say they haven't seen credible threats of increased violence at schools, but some have increased security following reports of warnings in TikTok videos.
The apparent social media threats had many educators on edge since they were circulating in the aftermath of
Some school districts stepped up patrols and alerted parents.
"We are writing to inform you and not alarm you," Oak Park and River Forest, Illinois, school administrators said in an email to parents. "We have been made aware of a nationwide viral TikTok trend about 'school shooting and bomb threats for every school in the USA even elementary' on Friday, December 17."
The administrators said local police departments would increase their presence around schools "out of an abundance of caution."
School officials in numerous states, including Arizona, Connecticut, Illinois, Montana, New York and Pennsylvania, said Thursday there would be an increased police presence because of the threats.
In Florida, Broward and Miami-Dade County Public Schools announced Thursday night that they'd increase law enforcement presence across their districts, CBS Miami reported.
BCPS first announced the precautionary move, though it noted that the "threat did not originate locally and is not believed to be credible."
TikTok tweeted that it was working with law enforcement to investigate. "We handle even rumored threats with utmost seriousness," the statement said, "which is why we're working with law enforcement to look into warnings about potential violence at schools even though we have not found evidence of such threats originating or spreading via TikTok."
A U.S. law enforcement official told CBS News there's no known credibility to the threats.
An FBI spokesperson told CBS News the bureau "takes all potential threats seriously. We regularly work with our law enforcement partners to determine the credibility of any threats. As always, we would like to remind members of the public that if they observe anything suspicious to report it to law enforcement immediately."
The Michigan State Police, among law enforcement agencies responding to the posts, said in a statement Thursday it was unaware of any credible threats.
CBS Los Angeles reports that the L.A. Unified School District, the nation's second-largest, said it's safe to send kids to school Friday but it takes all threats very seriously. Other districts in the region said they're aware of the threats and constantly monitor school safety.
At least a few districts announced plans to close school buildings Friday, including Gilroy High School in northern California. Gilroy police said they'd found threats on social media not to be credible, but school officials said final exams scheduled for Friday, the last day before winter break, would be postponed to January out of an abundance of caution.
"Making the decision to cancel classes tomorrow has not been an easy one," Principal Greg Kapaku said in a message to parents.
Many schools in the Houston area are barring student backpacks Friday, reports the CBS affiliate there, KHOU-TV.
In the Westchester County, New York town of Scarsdale, the schools superintendent told parents the posts "are believed to have originated from outside the United States."
"Every time a repost goes, it goes from town to town, it goes from state to state, so we don't know where the origin starts," Nassau County Police Commissioner Patrick Ryder told CBS New York.
The posts follow a disturbing trend that has had students acting out in response to social media challenges. In September, students across the U.S. posted videos of themselves vandalizing school bathrooms and stealing soap dispensers as part of the "devious licks" challenge.
In October, students were challenged to slap a teacher, prompting the National Education Association to call on the leaders of Facebook, Twitter and TikTok to intervene.
Internet companies such as TikTok are generally exempt from liability under U.S. law for the material users post on their networks, thanks in large part to the legal "safe harbor" they are given by Section 230 of the 1996 Communications Decency Act.
"It would be unlikely that TikTok would be liable if there were actually to be a shooting," said Jeff Kosseff, who wrote a book about Section 230 and teaches cybersecurity law at the U.S. Naval Academy. "Even without 230, there are just a lot of barriers against being able to bring a cause of action against the medium on which a threat was posted."
But Kosseff, who got a warning about the TikTok challenge Thursday from his daughter's school district in Arlington, Virginia, said that doesn't mean TikTok can't do something about it.
"They have a lot of flexibility to be doing the right thing and taking down harmful content. I am hopeful they are doing that," he said.
The threats outraged educators around the country.
"Whether done as a joke or with malicious intent, it's unacceptable. We know our school personnel will do everything in their power to keep our students safe," officials with the Iowa State Education Association, the Iowa Association of School Boards and School Administrators of Iowa said in a joint statement.
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