Schools in a Montgomery County district were closed Monday due to an investigation into a potential threat that was posted on social media but ultimately determined to be a "misunderstanding."

Classes in the Upper Perkiomen School District were canceled while authorities investigated a threatening post on Instagram, the district said.

That threat was deemed not credible and classes will resume Tuesday, officials said. Monday's after-school activities will also take place.

Police said the preliminary investigation found that the social media posting that prompted the closing contained screen shots from a video meant to curtail gun violence and identify warning signs of potential violence. That video was originally posted by sandhookpromise.org, an anti-gun-violence nonprofit founded by families of victims of the 2012 massacre at Sandy Hook Elementary School.

"We need to work together, as a community, to create a safe and supportive learning environment," Superintendent Alexis McGloin wrote in the message on the district's website. "We ask that you please discuss the day's events with your child, emphasizing the seriousness of this situation and the impact their on-line interactions can have on themselves, their friends, family and community."