MANITOWOC, Wis. (WFRV) – Classes were back in session at a Wisconsin middle school Monday after dozens of spiders forced it to close temporarily last week.

According to a statement from Wilson Middle School in Manitowoc, roughly 40 miles south of Green Bay, classes were canceled on Friday after a student and a teacher were reportedly bit by yellow sac spiders.

On Thursday, administrators say a student sitting in a classroom brushed a spider off of her arm. Officials say that there was no visible bite, however, her arm became itchy and swollen. The school nurse provided medical attention and the student’s parents were notified.

The statement also says that a teacher was recently bit and needed medical attention for swelling, itching, and pain.

Exterminators were called in to eradicating the more than 30 spiders found in several classrooms. It isn’t yet clear how they came into the building.

“This is the first time I’ve ever dealt with a spider issue,” James Feil, Manitowoc Superintendent, told Nexstar’s WFRV. 

In a statement, Principal Cory Erlandson said the school wasn’t aware of any other students or staff being bitten, but encouraged parents and guardians to “be on the lookout” for symptoms.

Yellow sac spiders are believed to be responsible for the majority of reported spider bites, Utah State University explains. Though their bites are not lethal, they can be very painful and typically cause burning, itching, or swelling. According to USU, nausea, fever, discomfort, stomach cramps, or skin necrosis can also occur, but are rare.

Mayo Clinic recommends seeking medical care following any spider bite if you were bitten by a dangerous spider, like a recluse or widow spider; aren’t sure whether the spider that bit you is dangerous; you experience severe pain, abdominal cramps, or a growing wound near the bite; redness or red streaks are spreading in the bite area; or you’re struggling to breath or swallow.