A vague threat posted anonymously Monday night, apparently on Facebook, caused a larger police presence on the Maricopa High School campus this morning.

Maricopa Police Department cleared the campus overnight after parents used the department’s mobile app to alert them to the post.

MHS Principal Brian Winter sent a message to parents at 5:30 a.m. notifying them of the situation and noting that school would remain open.

“Although we are unable to determine the credibility of the threat, keeping you informed is our priority,” he stated.

The post used a 2012 evidence photo from the Trayvon Martin murder case in Florida, showing a hand holding a gun, an image from Martin’s cell phone. The superimposed phrase “MHS kids better not —- with me tomorrow” was followed by a smiley face emoji.

Winter asked students to leave their backpacks at home today. “Bags and large purses brought to school will be checked and stored with administration.” Students who stayed home were not penalized for the absence.

“We are still investigating this matter,” MPD spokesman Ricardo Alvarado said. “We have reached out to FBI, the Mesa Fusion center and other intelligence-gathering agencies.”