Despite authorities dismissing a vague and viral TikTok trend warning of nationwide school violence on Friday as non-credible, widespread school closures, stretched law enforcement resources, and put families on edge ahead of a critical holiday travel season.

A number of school districts in states ranging from Minnesota to Texas announced school closures on Friday in response to a wave of videos, some mentioning specific schools, advising students not to attend class on December 17. Law enforcement in other areas was on high alert, sending officers to guard schools as a precaution.

The US Department of Homeland Security said Friday morning that it has no evidence to support the claims but urged the public to “remain vigilant.” According to Hilary McQuaide, a TikTok spokesperson, while the company is aware of vague warnings on its platform about possible school violence, it has yet to discover any original, specific threats of violence that may have prompted the viral warnings. The company tweeted on Thursday afternoon that it takes “even rumored threats very seriously.”

TikTok said Friday that it will continue to monitor its platform for suspicious activity, but that media coverage characterizing the viral trend as a threat to school violence may unintentionally encourage someone who is predisposed to act, creating the very risks that families are concerned about.

“We are deeply concerned that the proliferation of local media reports on an alleged trend that has not been discovered on the platform may end up inciting real-world harm,” the company said. According to a federal law enforcement source, authorities are most concerned that the rapidly unfolding social media narrative will inspire a lone offender to carry out an actual attack. The situation exemplifies the current threat environment in the United States, according to the source.

“This is an example of how social media and other communication platforms play a role in spreading threat-related narratives, which can then result in the need for escalated security measures in and around parts of our critical infrastructure,” said the source.

Little Falls Community Schools in Minnesota announced Thursday that it would close early on Friday after being “specifically identified in a TikTok post” linked to the warning trend. According to local media, Kaufman High School in Texas also canceled classes. According to local reports, Atlanta Public Schools said in a letter to parents that some facilities would beef up security on Friday, while schools in Polk County closed entirely.

Albemarle County Public Schools in Charlottesville, Virginia, said in a letter posted to its Facebook page that the TikTok trend is a reminder not to share posts about school violence.

“Even if they are not credible threats,” the letter stated, “they can cause a great deal of stress and anxiety for our students, families, and staff.” “Creating or disseminating such posts may also result in criminal charges.” We ask our families to keep an eye on their children’s social media activity and to talk to them about appropriate online behavior.”

In an email to families on Friday, NYC Department of Education Chancellor Meisha Porter addressed the social media challenge, saying it encouraged students to “call in bomb threats, school shooting threats, and other threats,” Porter emphasized the threats were not specific to only New York City and many of the posts are general and not specific to one school.

“Any social media posts of challenges involving threats or actions of violence against school communities will not be tolerated,” Porter’s email said. “Threats of violence have very real consequences regardless of the reason the threat was made, and we do not want our young people to jeopardize their bright futures over social media challenges such as these.”

Porter encouraged families who see threats aimed at specific schools to call 911.