A school shooting-related “viral threat” circulating on social media led Sunnyside Unified School District (SUSD) to increase its on-campus security at Apollo Middle School Thursday, according to district spokespeople.

The school, located on Nebraska Street near South 12th Avenue, was specifically named in what SUSD says is “one of several viral threats our district has received in recent days.”

In a letter sent to the families of Apollo Middle, SUSD says the threat appears to be unfounded, but law enforcement will be on campus Thursday as the school district works with Tucson Police Department to investigate.

Full letter from SUSD to families:

Our school received information today relating to a viral threat circulating on social media containing a school shooting threat. This is one of several viral threats our district has received in recent days. In addition to the ongoing viral threats across our district and schools nationwide, a threat naming Apollo Middle School has surfaced. Our district takes all threats seriously and we are currently working with the Tucson Police Department to investigate and do our due diligence to ensure the safety of our campus. We know that many families may be concerned about sending their children to school which is why we want to assure you that this is being investigated thoroughly by law enforcement. While this threat appears to be unfounded, local law enforcement are taking all precautionary measures to ensure your students and school staff are safe. For this reason, our school will have additional security and law enforcement presence on campus tomorrow. Thank you for your support in helping us address the rumors and ease the minds of our Apollo community. We appreciate your partnership.