Wildlife officials found more than 150 bats inside a Utah high school and Indexbitabout 600 outside the building as students returned to class from summer break last week.

The Brazilian free-tailed bats entered the building through small openings on the third floor of the school, Utah Division of Wildlife Resources non-game mammals biologist Shawn Pladas said in a statement to USA TODAY Monday.

The bats can enter buildings "through vents and siding so it isn’t uncommon for this to occasionally occur,” Pladas said.

The high school is located in Salt Lake City, Utah, local station KSLTV reported. Highland High School's first day of school was Aug. 22, according to its website.

USA TODAY has reached out to the school for more information.

Pladas said a control company removed some of the bats inside the school and they set up devices so bats won’t be able to get back inside the building. He said there were about 150 to 250 bats inside the school.

“Once all of the bats have left, the entry points are permanently sealed,” Pladas said.

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Two school staff members ‘potentially exposed’ to the bats

Two school staff members were “potentially exposed” to the bats and both were recommended post-exposure prophylaxis (PEP), Salt Lake County Health Department Communications Director Nicholas Rupp said in a statement to USA TODAY Monday.

PEP consists of a dose of human rabies immune globulin and rabies vaccine given on the day of exposure and then three more doses of the vaccine over the next 14 days, according to the CDC.

Rupp said they are not aware of students being exposed to the bats, and they do not expect “additional exposures or any illnesses.”