The creepy clown phenomenon appears to be reaching new heights in the Dallas-Fort Worth area.

Security at four high schools in Dallas — Spruce, Carter, Madison and Skyline — was ramped up Monday after clown-related threats surfaced on social media over the weekend.

#DallasISD Police and Dallas Police are investigating all leads relating to clown threats. We will continue to monitor & share information. — Dallas ISD (@dallasschools) October 3, 2016

The safety and security of students is our No. 1 priority. We are aware of the “clown” threats and the situation is under control. — Dallas ISD (@dallasschools) October 3, 2016

At Skyline High, a student was disciplined after wearing a clown mask during the lunch hour, a district spokesperson said.

That incident, coupled with the threats, triggered a "modified lockdown" at the school.

But Dallas school district Police Chief Craig Miller told KDFW-TV (Channel 4) most of the increased security Monday was part of scheduled, routine drug-dog checks.

He acknowledged the online threats but said he thinks some of the photos being shared originated outside of Dallas.

At Spruce High, a student reported seeing a clown tying balloons on cars in the parking lot, and parents dropping off their children said they received an automated phone message about the threats.

Security was also tightened at some Cedar Hill ISD schools on Monday after an Instagram post from "Billy the Clown" seemed to suggest he would be going to the school to cut people, police Lt. Colin Chenault said.

The officer said the threat may have been posted by a minor, but it drew the attention of district officials who made sure no kids were roaming the hallways during classes, and upgraded the police presence on the Cedar Hill High campus.

"Mr. Billy thought it'd be apparently funny to post some information about coming to Cedar Hill High School today,"Chenault said in a Facebook Live video.

He said police are thinking of a way to calm nerves over the clown threats.

"If we don’t do something early on it’s just going to drag all the way out until Halloween and everyone’s going to be really on edge," Chenault said.

Fort Worth, Garland, Richardson and Saginaw school districts were also investigating similar threats on social media.

The Garland district put its campuses on alert Monday but assured parents in a written statement that "these clown posts are a hoax."

While there have been 12 arrests linked to clowns-related mischief nationwide, some experts believe other sightings may be a simple case of mass hysteria.

In Fort Worth, police responded to a call Sunday night after a resident reported seeing a clown running down the sidewalk and yelling, according to WFAA-TV (Channel 8).

The call came around 11:30 p.m. to the 5800 block of Melanie Lane, in a residential area near Interstate 35W and Loop 820 in North Fort Worth.

Officers did not see the clown, and no report was taken, as they could not confirm a criminal offense had occurred.

In another sighting reported in Fort Worth, Kaelen Sherman said on Facebook that she saw two people in clown costumes driving through the parking lot of the Target on Alta Mere Drive, looking into car windows.

Richardson police spokesman Kevin Perlich said police received multiple tips about clown-related threats over the weekend, but as soon as police looked into them, the threats began to fall apart.

Someone vandalized J.J. Pearce High School in Richardson with a clown-related threat this weekend, but nothing came of that either, according to Perlich.

"We've made resources available to schools in the area to put them at ease, but there's nothing unusual going on," Perlich said. "There's no real disruption."

Social media page DFW Scanner claims about a dozen calls have come in reporting sightings in North Texas, but this has not been confirmed by police.

The supposed sightings comes after a string of reported clown sightings nationwide.

In late August, Greenville, S.C., residents claimed cash-waving clowns were attempting to lure kids into the nearby woods. Since then, reports have sprung up from Alabama to New Jersey.

In Houston, the Harris County district attorney's office announced Monday that a 14-year-old had been charged with making a terroristic threat against a Houston ISD school. Officials say the student — whose name was not released — made the threat on social media and used an image of a clown.

Staff writers Caleb Downs, Corbett Smith, Tom Steele and Claire Cardona contributed to this report.