Update 1 p.m.: Sioux Falls School District spokesperson Carly Uthe said as of 1 p.m, the district has not heard any more news about who might be behind today's threat against students at Roosevelt High School.

However, parents have started to take their children out of the campus as a precaution and some students have chosen to leave on their own.

Because the district made the decision to keep the day running as normal, time missed will be counted as an unexcused absence for students who leave without their parent's permission, Uthe said. If parents call into the school to excuse their children, it's considered a 'parent request" and is an excused absence, she said.

Uthe couldn't speak to how much of a decrease in attendance the school has seen.

"It's the student's choice to leave the school, but there's nothing different about the school day," she said.

Earlier story:

The FBI and local law enforcement officials are investigating an overnight threat made to Roosevelt High School via social media, Sioux Falls police spokesperson Sam Clemens said.

"It's hard to know if this is credible at this point," Clemens said. "Obviously, it's early on in the investigation, but it does seem there are some similarities between other threats we've had in the past."

This is the fifth possible threat involving a Sioux Falls school since the school year started in August.

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The district has heightened security at the campus for the day, but classes are continuing as normal, district spokesperson Carly Uthe said at about 8 a.m. Though it is Election Day, Roosevelt is not a polling place, so school officials aren't expecting an influx of extra visitors at the campus, she emphasized.

The threat was posted to a Sioux Falls Reddit thread at about 4 a.m., by someone with the screen name SchoolBsho. Sioux Falls police first received notification about the threat at 4:45 a.m., and were still receiving numerous calls about it as of 8:45 a.m., though Clemens couldn't quantify the amount.

Earlier:Brookings student who wrote threat didn't have intent to carry it out, officials say

"Tomorrow I'm going to do a school shooting at lunch," the threat stated. "I hate my boss. Kill the student with a gun. Roosevelt high school SHOOTING 11-06-2018."

The threat was also screen grabbed and reported to the police department on Twitter, but police have yet been able to confirm any credibility to it, Clemens said.

"It's certainly possible, but we don't know if it's connected to a student at this time," Clemens said. "Our forensics guys are working behind the scenes, and I imagine the FBI is doing the same thing on their end. Obviously, there is a sense of urgency to identify the person to figure out who is posting this and why."

In a further comment on the thread, a person with the screen name Schoolboot responded to comments against the threat stating,"[Explitive] everyone in this world. This is going to be real."

"I'm going to kill the student and everyone," the threat goes on to state. "Roosevelt high school to Hell. I'm going to shoot at lunch 11 a.m. 11-6-18. Please call the police. Let them know there will be a shooting at the school."

The original post has since been locked so no further comment can be added.

Additional threats have been made on Reddit and on Twitter, and police believe they may be done by the same person, Clemens said. Despite the other posts, law enforcement and school officials said they are not changing how they approach the situation because there was nothing credible to indicate the need to do so otherwise.

That includes closing school, having students shelter in place, evacuating the campus and placing a campus on lockdown, all of which is the school district's decision, Clemens said.

However, law enforcement won't stop investigating until a person is identified, he said.

"Other than those messages, we haven't had anything credible that has led us to think this is going to happen," Clemens said at a 10:30 a.m. police briefing. "But we're certainly taking precautions to be safe."

Despite precautions, some parents chose to take their children out of school for the day or students chose to leave one their own.

However, because the day was continuing as normal, time missed by students who leave on without their parent's permission will be considered an unexcused absence, Uthe said. If parents call into the school to excuse their children, it's considered a 'parent request" and is an excused absence, Uthe said.

The district also sent an email to parents at about 8 a.m. Tuesday morning, stating law enforcement and federal officials were conducting the investigation, but district officials did not know much more information outside of that, Uthe said.

She could not speak to how much of a decrease in attendance the school had seen during the day.

Earlier:Police: Student in custody after making social media threat against schools

"At this time, all we know is what was sent out in the email to parents," Uthe said. "We're just letting the police take care of the investigation."

District officials will provide more updates as details become available, the email to parents read. Police and school officials encouraged that the public continue to stay aware report anything suspicious or out of the ordinary.

"Our foremost goal is to keep our students and school community safe, and we appreciate your support in doing so," the email to parents stated.

And the official Instagram account for the high school made a statement mid-morning, showing no fear in the face of the threat.