Plano police investigating threat at Clark High School

A high school in Plano is dealing with a school shooting threat on top of its existing election day safety concerns. 

In a letter to parents, Clark High School administrators confirmed police are investigating a threat that was posted on social media overnight. It implied potential violence at the school on Tuesday.

"As the investigation is underway and potentially involved students are being identified, we will have an additional security presence on campus today," the school said.

There were several police vehicles parked outside the school Tuesday morning as worried parents pulled their kids out of school.

The school is also a voting location and is expected to have an influx of visitors during school hours.

RELATED: Some North Texas schools closed for election day

Plano ISD said it has a security plan in place for the midterm elections. For example, the district hired off-duty law enforcement officers to patrol the 29 campuses serving as polling sites.

"Well, there’s a lot of reasons why it’s gotten to this point. In the past, there’s been issues in Texas and I think you should always be ready on election day," said Jeffrey Blackburn, a Plano voter.

Some other North Texas school districts like Dallas, Fort Worth, Richardson, Garland and Lewisville opted to close for the day, citing election day security concerns.